Feb 4 2019
German state museums stock an innumerable number of historical coins that vary from one another merely in details. These archaeological artifacts are different from paintings and may not be barcoded, marked, or labeled.
Scan of the base color of a coin issued by Konrad, Margrave of Meissen and holder of the coinage prerogative, mint date ca. 1150. (Image credit: Fraunhofer IFF)
In association with the Saxony-Anhalt State Office for Heritage Management and Archaeology, a research team at the Fraunhofer Institute for Factory Operation and Automation IFF has created a new scanner and analysis software, which digitally capture the coins’ visual features and precisely describes them in just a matter of seconds. The unique scanning system can be utilized for recognizing and identifying coin finds.
Fake or Original?
Even professionals with a trained eye find it difficult to answer this question with regards to historical coins. For example, how to recognize the forgeries returned to a museum rather than the actual coins loaned for an exhibition? How to prevent mix-ups and switches among objects loaned by museums? At the Saxony-Anhalt State Office for Heritage Management and Archaeology, staff members were also looking for answers to these questions.
About 20000 coins, usually a few centuries old, are kept in the vaults and archives of the State Office. This collection of coins is continually expanding, and added to this, this unmanageably wide range of historical coins has been painstakingly documented and recorded manually, until now. The coins, unlike paintings, may not be barcoded, labeled, or marked. Looking for a solution to this dilemma and also as part of the state of Saxony-Anhalt’s digitization campaign that comprises of the digitization of historical coins, archaeological finds, and cultural heritage, the State Office sought the help of the Fraunhofer IFF in Magdeburg.
Digitally Fingerprinting Archaeological Finds
“The State Office aimed to digitize its complete numismatic collection. This gave rise to the idea of creating a digital fingerprint with which individual coins can be recognized and classified—much like facial recognition of people. The fingerprint replaces the bar-code as it were,” stated Dr Christian Teutsch, a research scientist at the Fraunhofer IFF, describing the initial contact with the State Office for Heritage Management and Archaeology.
The partners worked closely and eventually developed an advanced software analysis system and a visual data acquisition system in their project called, “Digital Fingerprints of Archaeological Finds: Artifact Identification and Recognition Prototype”, which accomplishes this by digitizing and precisely detailing the old coins and also acquiring exclusive signatures from the coins. The new scanning system had to work in a contactless manner, achieve a recognition rate of 98% or more, and obtain the data of both faces. Silver, gold, copper, and bronze coins with diameters ranging between 5 to 75 mm were tested.
Detecting Forgeries
The innovative scanner, Optical System for Coin Analysis and Recognition, or O.S.C.A.R in short, scans the visual features of the coins and also the tiniest signs of wear like clipping, scratching, edges, contours, denting, and pitting, which all make an object special. This factor is very important to recognize an array of coins of the same type. “Obviously, changes can be detected when a coin is scanned twice. This makes it possible, for instance, to check upon the return of loaned coins whether scratching has occurred, the artifact has been damaged or even if it is a fake,” stated the engineer, a staff of the Measurement and Testing Technology Business Unit.
Variable Light Source Adjustment on the Digitized Coins
The scanner includes a number of cameras and also several light sources illuminating the coins from various directions, thus enabling high-precision magnification and resolution. This allows Teutsch and his group to emphasize and scan each feature of the coins without any reflection or glare.
The light sources can be rotated on the monitor virtually and moved over a coin’s surface as desired. That is a major benefit for numismatists, who will now be able to identify only poorly recognizable obverses and reverses much faster and more precisely.
Dr Christian Teutsch, Research Scientist, Fraunhofer IFF.
The digitization process itself is quite easy: After scanning the barcode on the specific bag belonging to every coin, the coins are positioned individually under the scanner. The device can be started by simply pressing a button. A uniquely designed optical analysis system recreates the surface features and color of the historical artifacts. The scanner is able to capture more than 1000 visual features for each coin, and the images, thus recorded, are inferred as measurement data. In addition, color charts and reference samples ensure that the color space of each image is similar and that the image itself is also standardized. This process makes sure that these image data can be evaluated against various institutions. In the subsequent step, the entire measurement data are sent to the analysis software, which applies the data to calculate the digital fingerprint.
The software compares coins using the database, i.e. searches for their signatures. There was no way to identify them earlier. Knowledge about the find location and other information were lost if a bag fell onto the ground and the coin fell out.
Dr Christian Teutsch, Research Scientist, Fraunhofer IFF.
Now, the museums and cultural heritage agencies of the states can make coin finds accessible even to the general public. In addition, all coin databases of the states can be validated. Moreover, association with the national KENOM coin database is being taken to an entirely different level. The digital data can be used by numismatists to ascertain correlations among various types of coins, or identify locations and thus useful historical contexts.
10000 Coins Already Digitized
With the help of the unique scanning system, the numismatic collection can possibly be digitized and documented automatically, thus speeding up the arduous work dramatically. Already 10000 coins have been scanned by the project partners, and the entire collection of 20000 specimens will be digitized shortly.
An initial presentation of the prototype had suitably impressed the numismatists.
“The new scanning system will revolutionize numismatics in Europe,” stated Teutsch, summarizing. Since the system is also capable of capturing brushstrokes, it could be extended to inspect paintings as well, which is the best part about it. While paints can be forged, exact brushwork cannot. “We detect any Van Gogh with our solution, guaranteed. A forgery would be immediately identifiable because of discrepancies in the details of the application of paint and ridges caused by brush bristles.”