Three-dimensional reconstruction of Roman coins from photometric image sets

“Three-dimensional reconstruction of Roman coins from photometric image sets”, a 2017 Journal of Electronic Imaging paper by Lindsay MacDonald, Vera Moitinho de Almeida, and Mona Hess.

The present study combined two datasets representing the surface topography of the two Faustina coins (Fig. 1). First, they were scanned by a 3-D color laser scanner, producing a point cloud of the surface shape. Second, they were photographed in an illumination dome with directional lighting. The two representations were combined to produce a digital elevation map (DEM) of each coin with the accuracy of the scanner and the fine detail of the photography.

The Insane Million Maker Master Counterfeiter

Good documentary storytelling on counterfeiting: Snap Judgement recently made a 22 minute segment about Frank Bourassa, a Canadian who counterfeited a quarter of a billion US dollars in twenties in 2009.

I calculate that $200,000,000 in $20 bills would weight 10 tons and would completely fill a 12' moving van.

NGC population reports for graded ancient coins

Catalogers of high grade modern coins often boast about coins having only a few specimens, or even no specimens, known in a higher grade.

Ancient coin catalogers will sometimes say "finest known" but they rarely say things like "only a population of 43 coins better".

On NGC's slab verification pages, for example https://www.ngccoin.com/certlookup/4629247-016/NGCAncients/, there are no population reports comparable to modern coins. That page says "Total Graded by NGC: Not Available".

Yet I noticed the Heritage Auctions web now includes NGC Ancients population reports. I noticed this watching their Long Beach auction yesterday. Here is an example from a recent Heritage online-only auction: https://coins.ha.com/itm/ancients/g...m-9h-ngc-ms-5-5-3-5-test-cut/a/231836-61011.s . The auction listing displays the slabbed population with the grade of the current lot highlighted in yellow.

Here is the owl population as of September 7th 2018:

The auction house gives an NGC population report and includes the count ranked star (= "impressive"). They don't mention "fine style" or "test cut" or the x/5 ratings. This particular lot has a huge test cut that doesn't make it into the numerical chart.

I was curious to see the single starred "Choice MS" example in the above population report. It is https://coins.ha.com/itm/greek/anci...22-gm-5h-ngc-choice-ms-5-5-5-5/a/3066-30035.s, and it sold for $36k last month.

Replica hobo nickels

Is anyone familiar with Chinese hobo nickel replica maker Gyphongxin? The e-Sylum discussed Chinese hobo nickel replicas but I still meet advanced collectors who do not know the scope of it.

I purchased the "hobo dime" above with the Medusa skull design last year. It looks like a 1916-D. Often the creations of the artist (or artists?) "Gyphongxin" duplicate award winning hobo nickels but I haven't found the prototype for this one. A store on Alibaba.com is selling these for $1.70 and they say they have 9837 pieces available. The seller also has one with a 1916-S reverse with 9995 available.

In hand the coins don't look particularly great. Other Chinese replicas do look great. I recommend anyone interested in the Chinese replica coin production quality listen to Charles Morgan interview Beth Deisher on the CoinWeek podcast.

There is a new wrinkle in how the coins are being shipped. The half-dollar at the top of the page sold on eBay for $4 with free shipping. It shipped from China to the nation of Georgia. (Not the US state, the former Soviet republic.) A different shipper slapped a sticker with a return address in Tbilisi over the first sticker. This process caused the replica to take six weeks to arrive. Why is the seller is willing to pay for double postage and send the coin around the world the long way? I suspect US Customs authorities are looking for and stopping these replicas.

I recommend everyone check out this Alibaba.com store. Perhaps the ancient Greek and Roman coins won't fool you. Perhaps the US coins or the world silver won't fool you. There are a few things in this store that look very good in a photo and sell for a dollar or two.

The Feather Heist

Good reporting on museum security: This American Life recently made an hourlong episode about the 2009 smash-and-grab burglary at the Natural History Museum, London. Bird carcasses and feathers worth more than $1,000,000 on the fly-fishing black market were stolen. Some have been recovered.

Iceland

If your are interested in coins there is little to see except the Numismatic Museum. The museum is a single room in the Central Bank of Iceland building. The room is open weekdays 1pm to 4pm. It is across the street from the Harpa concert hall and borders the park with Einar Jónsson’s statue of Viking settler Ingólfur Arnarson.

The highlights are Halldór Laxness’s Nobel Prize medal and Thröstur Magnússon’s plaster design for the 100 kronur coin along with an obverse die.

There were no Viking coins on display.

Iceland’s 1930 Althing commemorative coins were on display. I had seen photos of these coins but the real ones look much more impressive than the photos.

I would have liked to purchase collector coins. (Some central banks, such as Ireland, have a retail window for collectors.) The guard at the Iceland central bank did not know about coins and the curator of the museum was on vacation at the time of my visit.

Other than the museum there is not much coin-related to do in Iceland.

Coins are still in use but I wasn’t getting many of the smallest denominations in change. At the nearby Landsbankinn bank branch I found a vending machine for coin rolls. The machine is labeled myntrullur which I believe is the Icelandic word for “coin rolls”. It seems to be a rare word — a Google search did not find a single instance. (Web searched found 20k examples of the related Norwegian word myntruller.)

I went to the Kolaportið flea market to look for obsolete coins. I found a booth stocked with stamps and banknotes but not coins. There was a booth with miscellaneous circulated coins of many countries, mostly Iceland, to pick from for a few kronur. That booth also had a single partially-filled coin album with holes for all of the coins issued by Iceland up until 1970. This album would have been an interesting numismatic souvenir but soft PVC held the coins in place and many had turned green.

Another booth at the flea market had a few uncleaned Roman coins. These were not Icelandic finds and the vendor wanted the equivalent of $30 each for them.

Many of the gift shops in Iceland have sets of obsolete coins. The coins for sale are exactly what is offered by http://www.lucky-coin.com/coins although the prices are about 3x what is listed on that site. The frustrating thing about these sets is the mixed condition of the coins. There will be nice AU-grade coins alongside cleaned G coins. It would take several sets together to make a nice set. Also, most of the holders are wrapped with soft plastic so there may be PVC concerns.

There is an Iceland Numismatic Association but they don’t meet in the summer. I also tried to contact two eBay sellers based on Reykjavic but there were out of town.

Iceland's circulating coins are nice. They depict fish. Coins aren't issued every year. Some of the coins I received in change were in great condition even though dated 2011 or even earlier.

Anti-pollution medal by Vasco Berardo

Another anti-pollution art medal.

Portugal, 1974. Vasco Berardo (1933-2017). 95mm. Mintage 400

Obv: Poluição / Cavaleiro do Apocalipse (=Polution / Horsemen of the Apocalypse); Bust wearning gas mask and headphones; demon birds behind; artist's signature below. The entire field engulfed in poisonous vapors.

Rev: Caped rider wearing armor and shield on left arm, holding wrench in right hand, riding right on armored horse motorized horse through wisps of pollution.

From a series of six horsemen. Pestilence is one of the original four horsemen described in the Biblical book of Revelation. In Berardo's vision the horsemen are Peste (Plague), Fome (Hunger), Poluicao (Pollution), Morte (Death), Guerra (War), and Droga (Drugs).

Anti-pollution medal by Isolino Vaz and Luciano Inácio

(Image from medalhasportuguesas.wordpress.com, a Portuguese medal blog.)

For Earth Day (April 22) here is an anti-pollution medal from my small art medal collection.

Portugal, 1972. Designer Isolino Vaz (1922-1992), Engraver Luciano Inácio. 80mm, 272g

Obv: Poluição (Pollution); bust of a malnourished and bald figure, turned to the right, with the hand on the forehead in sign of agony.

Rev: Girl with braids and school gown kneeling plants a tree in the ground. Next to you a shovel. Behind, four flowers, two on each side and in the sky are three stylized figures of birds.; Salve Mos o Mundo; Valadares - V. N. De Gaia / 30-VII-1972 (Save the World; Valadares - Vila Nova de Gaia - July 30 1972. Valadaras was a parish in Gaia city.)

Edge: 147 / 500

Note: This medal was executed in the workshops of João Baptista Cardoso, for the initiation of the Promoting Committee "Recordar é viver" (Recall is living), formed by former students of the primary schools of Vila Nova de Gaia. 500 examples were made in bronze and another 20 in silver, distributed by the "Galeria Arte e Medalha", in Oporto.

Ball Terminal

Here is the inscription on a coin of Mithradates the Great, circa 85-75 BC. (Not mine. A dealer photo.)

The characters have circles at the ends. If the ends had been lines we would call them "serifs". Many years ago I tried to learn the term for characters with circles on the ends but eventually gave up. Today, while reading an article on the typography of James Mitchener's novel cover art, I stumbled onto the term “ball terminal”.

Exactly what I was looking for. Now I can search for this term ... and find very little.

Recording provenance in the blockchain

An October 2017 article by Peter B Campbell in The Guardian, “Archaeology and blockchain: a social science data revolution?” discusses using blockchain, the computer technology that ensures Bitcoins are not counterfeited, to record provenance data for antiquities.

Campbell is an archeologist and his article mentions Islamic State and blood antiquities. Those claims might be overblown but the technical scheme described by the article seems workable for medium and high values items. The startup Kapu already conducted a test of using a digital 'coin' to create a provenance ledger.

Were an artifact to have a blockchain record, each time it crossed a border or was sold to a new collector the record could be updated to show it was legitimate. Conversely “blood antiquities” would have no record and faked records could not be manufactured as they often are today. Border security could then compare records of artifacts declared at customs to databases such as INTERPOL.

Some of the ideas, like swabbing antiquities with synthetic DNA, seem fanciful. The basic claim seems solid. Using blockchain technology for art isn't science fiction. An article by Jason Bailey on Artnome explains that the technology is already in use for proving ownership of digital artworks. Verisart and Codex are startups in this space. They hope to convince auction houses to use their technology to record sales.

Codex Protocol is designed as industry infrastructure for art and collectibles. So it's fine wine, classic cars, jewelry, fine art, anything else that sort of fits into that category of items.

For ancient coin collectors one problem is that we would like to be able to prove ownership before 1970, or before the 2007 agreement between the United States and Cyprus. These technologies are for recording transactions now, not 50 years in the past. I would be interested to learn what the legal community thinks of these things.

The SciTech Lawyer, a publication of the American Bar Association, just published an article on that very topic. Unfortunately for me, law professor Derek Fincham's article “Can Blockchain Technology Disrupt the Trade in Illicit Antiquities?” is not available to non-subscribers.

In the comments section, discuss if you would be interested in using blockchain to record your ownership of coins, and if you would pay a premium to know the previous owners of a coin back to 2019.

Himyarite coin with ancient South Arabian script

Unicode has included letters for the ancient South Arabian script used in Himyarite coins for a long time but I have never seen them used except in sites about Unicode itself.

Here is a coin from mint 𐩧𐩺𐩵𐩬 (=RYDN, Raidan/Raydan, at Zafar in Yemen).

I am not sure what is needed to use South Arabian script on your computer. I have a nice font of them on Mac OS 10.12 rendered under Safari but not under Chrome or Firefox.

The mint name, Raydan, is encoded as follows:

𐩧 = R
𐩺 = Y
𐩵 = D
𐩬 = N

I had more difficultly with the name of the ruler. It is 𐩲]𐩵𐩬𐩽𐩨𐩺𐩬 (= ʿMDN BYN, Amdan Bayyin Yanuf). Two of the letters on the coin did not make sense.

𐩲 ?= is this ʿ (Ayn, the rough breathing mark)?
] ?= I couldn't find this one in the table
𐩵 = D
𐩬 = N
𐩽 ?= This looks like their digit 1, but I couldn't find any reason it appears here.
𐩨 = B
𐩺 = Y
𐩬 = N

HIMYARITES. ‘Amdan Bayyin Yanuf, 2nd century AD. AR Scyphate Quinarius (1.16 gm) of Raidan mint. 13mm Obv: Male head right, within torc Rev: Himyarite/Sabatean legend 𐩲]𐩵𐩬𐩽𐩨𐩺𐩬 ʿMDN 1 BYN 𐩧𐩺𐩵𐩬 RYDN; Small male head, monogram to left, scepter symbol (or monogram?) to right. Ref: Sear, GIC 5717. Munro-Hay 3.2ai. ex-Pegasi Numismatics, Auction XXXIV, May 2016, lot 243 (unsold)

I don't actually have Stuart Munro-Hay's book Coinage of Arabia Felix so I have been using his article “The coinage of Shabwa (Hadhramawt), and othe ancient south arabian coinage in the national museum, Aden” which is available online and includes information on inscriptions.

I would be curious to know which computer/browser combinations can see the ancient South Arabian characters above. I would also be curious if anyone knows the correct Unicode way to encode the letters I am uncertain of.

XRF testing

At the ANS seminar Counterfeits: the Threat to Collecting and Scholarship several people from the museum community remarked analyzing the metal in coins using X-ray fluorescence (XRF). This technique is said by some people to be nearly as good as other techniques that are much more expensive.

If a coin contains modern elements, or if a coin has a different composition than a large group of known genuine coins, then it is likely false.

I asked who can provide such a service to private collectors — but no one had recommendations.

I received an unsolicited email recently from Phil Keck at Artemis Testing Lab. They offer XRF on ancient materials for $200. Two samples per item.

An eBay search found a service in Flushing Queens that will test coins (or anything else) for $20 a sample. The auction picture shows a Niton XL2 gun. Such guns can be purchased for $15-20k. I believe they can be rented as well. I am not sure how common such services are. A friend told me several years ago of one in a coin shop in Louisville KY.

If anyone has submitted ancient coins for XRF testing I would be curious to see what kind of reports you received and if they were helpful. If anyone is near New York and wants to try the service in Flushing or knows of a similar one perhaps a field trip could be organized to test coins. Any takers?

Black Sea Hoard dies

The American Numismatic Society hosted a seminar on Counterfeits: the Threat to Collecting and Scholarship with presentations by David Hendin, Robert Hoge, and Ute Wartenberg.

For me the most exciting part was inspecting dies from the group of counterfeits known as the “Black Sea Hoard.” In his book Counterfeit Studios and Their Coins Ilya Prokopov describes this hoard as the work of “Studio ‘Varna-1’”. The dies are said to be the work of a single master engraver. Coins produced by these dies were sold openly in museums as replicas. They were also being sold as genuine to collectors.

These dies represent the mints of Apollonia Pontika, Mesembria, Istros, and Chersonesos. The Chersonesos dies troubled me because they were unfamiliar. I recognize the style of the Varna-1 engraver's work on facing head coins. The Chersonesos dies are by the same sculptor. My inability to recognize them proves my understanding of that style of the artist's facing head fakes is overconfidence. I am not sure I would recognize fake Chersonesos coins without carefully consulting a scarce pamphlet-book Modern Forgeries of Greek and Roman Coins by Dimitrov, Prokopov, and Kolev.

The difficulty of photographing gold coins

Here are six professional pictures of the same coin.

These pictures appeared on the auction catalog or web sites of numismatic auctioneers Harlan J Berk, Classical Numismatic Group (twice), Heritage, Stack's Bowers, and the coin grading company Numismatic Guaranty Corporation.

These images were taken over the span of eighteen years. The version with the red background was scanned from a printed auction catalog. All of the other images are taken directly from auction sites or the slab company's slab verification image.

This coin did not change color in the last 18 years. Something about the lighting situation and the camera's color profile was different enough that each of these pictures is different.

What color is the coin really? In my memory the coin looks like the middle coin on the left-hand side. Yet when I held the coin over my computer monitor in a room lit by compact florescent lights it looked most like the upper right image.

Can the output of my computer be trusted? In the days of CRT monitors the color balance could be tuned and there were reference images for that purpose. LCD monitors are not as color-accurate as tuned CRT monitors. Perhaps I should repeat the experiment in the sunlight? Bottom-line: I am not certain which image is the most accurate.

Database of Digits Extracted from (modern) Coins

Xingyu Pan and imageLaure Tougne have published a paper describing their database of digits extracted from scans of modern coins.

The database of 3000+ images itself cannot be directly downloaded. They explain here that you may request it from them.

The paper is good! The databases discussed are

• 606 digit images manually cropped from high-resolution photographs of well-conserved coins
• 1,200 digit images automatically extracted from a subset of a PCGS database containing coins in different states of preservation
• 1,200 digit images manually extracted from the same coin photographs as above

Although the new dataset only contains digits from modern coins the authors discuss the literature of recognition of ancient coin lettering. There are as yet no public databases of images of the digit or letters extracted from images of ancient coins.

Antiquities Memorandum of Understanding with Libya

Please read Cultural Property Observer and comment on the Libyan MOU. If the MOU is completed and includes coins it will become difficult for Americans to buy ancient coins from Kyrene in European auctions. It will also be difficult to import Ottoman coins from the territory of modern Libya.

Do it this weekend or it will be too late.

Recognizing Roman coins with neural networks

Jongpil Kim of Rutgers university reports a neural network capable of correctly recognizing the emperor 73% of the time from coin images. The reverse type is recognized 67% of the time.

The report is available on SEQAM and the paper is available by clicking PDF on this Cornell library site.

Ancient Astronauts

Mike Markowitz covers The “Alien” Coin for CoinWeek.

Video on creating 'coins' with CNC machine

I stumbled across this 9 minute video which shows the process of creating a medallion with realistic bust using a CNC machine.

The medallion produced looks quite good! It looks better than most of the 'coins' featured in do-it-yourself coin making videos. Yet most of the steps made me cringe because I was certain he was doing it the wrong way.

Once he has a 3D model on the computer, he feeds a block of metal to a CNC machine rated only for wood. I was sure something would go wrong but he got it perfect.

To produce the round shape he just takes his metal block and starts hitting it with a belt sander! I was certain he was doomed but it looked very nice when complete.

To give the appearance of patina he uses spray paint. I was amazed that this worked at all! He got a nice effect in the end.

The final medallion suffered a bit of a 'staircase effect' on the face due to the limited depth control. I would have liked to see if he could have removed that with a bit of polishing. Even with the depth artifacts he managed to produce a pretty nice medallion using techniques I would not have expected to be effective.

Print on demand catalog of the coins of Troas

I recently purchased a Print on Demand copy of Warwick Wroths 1894 catalog of the British Museum collection Catalogue of the Greek Coins of Troas, Aeolis, and Lesbos.

Google scanned three copies of this book: from the University of Michigan, from the New York Public Library, and from Harvard

The Harvard copy doesn’t seem to show up in an ordinary Google Book search. I found it using this link: http://fig.lib.harvard.edu/fig/?bib=002349380.

Public domain books that have been scanned by Google can be printed on demand. To order online, just bring up the book in Google Books, click “Get this book in print” and “On Demand Books” and several vendors appear. I wanted to see an Espresso Book Machine in action. There is one at the McNally Jackson bookstore in Manhattan. So I went down there, armed with the title.

The machines aren’t self serve. I gave the operator my title, and he brought up the University of Michigan Copy. I had hoped to see it printed but the machine apparently takes a while to download the book. It downloaded overnight and the operator printed it the next morning. I was surprised to find I had received Harvard’s copy.

The problem with getting a different copy than expected is that Google’s 2008-9 analysis did a poor job of distinguishing photo plates from line art. For numismatic books this is a problem. If the Google book preview shows a coin “posterized” the print on demand copies print it as a black blob. Luckily Harvard's copy is better than the U of M's.

Here are three copies of plate 8. On Harvard and the NYPL’s copy, coins #1, #2, #18, #19 and the reverse of #22 are shown greyscale. On the U of M’s copy, none of the coins are shown greyscale. They all appear as “posterized” four color art.

The “posterized” coins appear as black blobs when the Book Machine prints them. I am not certain this is the fault of the book machine. It is unfortunate that there is no way to supply feedback to Google books that a page or part of a page is greyscale artwork.

There is also no way to specify that the printed size of the page is meaningful. This is not a huge problem for the BMC volumes, which originally appeared the similar in size to what the Espresso Book Machine prints.

I paid $17 plus tax for this volume. For comparison, the hardcover decent plate Italian edition by Forni from the 1960s can be found used for $50, with other copies selling for more. The original version can sometimes be found at auction for $150+.

Many years ago I wanted to get folks with original BMC volumes to scan the plates. I had hoped to assemble a plates-only PDF. I managed to scan a few volumes myself but was not able to get the needed volumes and the project fell through. Perhaps with the British Museum putting their collection online the need for this has passed?