• Coins & Medals

Minting anomalies

A coin has undergone a very complex process before it actually rolls off the presses. First of all, the image to appear on the coin has to be designed – sometimes based on an existing engraving and sometimes a new creation. Then two separate dies have to be produced somehow, one for the obverse and the other for the reverse of the coin, both bearing a negative engraving of the images. In the past, that was done by hand and to actual size. Moreover, every time that a die became worn or cracked, a new one had to be produced from scratch. If the coins were to be produced by several different mints, it was necessary to produce a number of identical dies simultaneously. This was extremely precise, time-consuming and above all very cost-intensive work.

Nowadays things are done very differently, making use of automated techniques wherever possible. The human touch still plays a very important role, however, and will continue to largely determine the quality of the end product.

At the Royal Dutch Mint (Koninklijke Nederlandse Munt [KNM], formerly known as Rijks Munt) an accurate sketch of the design is prepared which is four times bigger than the end product. This sketch is then ‘reversed’ and redrawn in its mirror image. The sketch is then transferred onto a slab of plaster.

Using the lines left in the plaster, an engraver can now work on the model to create a relief. The engraving must be done extremely carefully because the depth of relief on the final coin may not be more than one tenth of a millimetre! In the case of the national Dutch coins, the parts of the design that have an even relief, [L1] such as letters and beading, are added by machines nowadays. A flexible rubber mould is used to create a plaster model. This model is slightly convex because the resulting master die [L2] needs to be slightly convex too in order to allow the metal to be pressed into the recesses better when the coin is being struck. This is then used to create a concave positive mould from epoxy with a very hard top layer. Then, a so-called reduction punch or pantograph is used to reduce the model to the actual size of the coin and immediately transfer it onto soft steel. This is a very time-consuming two-stage process that takes around 30 hours altogether! The resulting upwards die [L3] is then subjected to various different treatments such as hardening and polishing before it can be used to produce the actual coining dies. In turn, these working dies are subjected to many other processes before they can actually be used to produce real coins. This is necessary to ensure that all the coin dies look the same. For more details, see the KNM’s 1984 Annual Report.

3 Gulden design 1800 (LSch.113)


Because a coin can turn out looking very different from a sketch, in the olden days it was common to make dies for the production of just a handful of coins from the relevant material – whether from standard or more unusual metal or sometimes even from cardboard – in order to better evaluate the design. In this database, the term ‘design’ refers to the end product and not the sketches and suchlike leading up to it.

25 cent 1817 niet en wel in de ring geslagen (LSch.288d)

Sample or proof coinage:

Once all the preparations have been made for the general transfer of the design, it is time to make a start on producing the actual die. It can sometimes be difficult to assess the quality of the die. For example, tiny hairline fractures may be present that are invisible to the naked eye. Striking samples reveals whether the die is up to scratch. That is why proof coinage is produced, sometimes (but not always) from the relevant material and sometimes on a blank planchet. In other words, sample coins are produced in order to better evaluate the die.

Gold off metal strike van 2½ Gulden 1874

Off metal strike:

In the case of an off metal strike, the original working die is used to strike coins in metals other than the originally intended one. For example, there is an off metal strike of a silver guilder coin in bronze, and an off metal strike of a silver 10 Cents piece in gold. Off metal strikes produced in a higher-value metal than the original coins are often of special value for collectors or intended as a gift for high-placed officials. Off metal strikes in a lower-value metal are usually produced so that the authorities can approve the design.

Restrike Gouden Rijder 1750


A restrike is a coin that is produced by the eligible Mint later than is indicated on the coin itself and is not intended for domestic circulation.

1 Gulden 2001

Mint-made errors:

Mint-made errors are flaws caused by problems with the machinery, die or blank during the minting process. Although strictly speaking every deviation from the intended result could be described as a mint-made error, this term is generally used for excentric strikes – in other words, the planchet was not positioned in the exact centre beneath the die which has created an oval or even teardrop-shaped coin – or for when the planchet was too thin which prevented the die from sufficiently striking the blank, resulting in the image being only vaguely visible (if at all). In reality, errors like this should not occur in modern coin minting – and if they do occur, the Mint should withhold them. Nevertheless, such coins do make it into circulation occasionally. Because collectors are always prepared to pay a little over the nominal value for Mint-made errors, I believe that some Mint-made errors have been produced on purpose in the past – or at least the coins have been knowingly released by the Mint.

½ franc Napoleon (LSch.182/183)


An incuse strike is an unintentional outcome and is actually a Mint-made error. When the die is raised, the previous coin can inadvertently remain stuck to it. The next blank is struck with that previous coin, meaning that it is only minted correctly on one side and receives an incuse impression of the image from the previous coin on the other. The word ‘incuse’ originates from French and means ‘hollow’.

1 cent 1828 U (LSch.334)

Double strike:

This is more or less a variation on an incuse strike, and is also a type of Mint-made error. Instead of being replaced by a new blank, a coin remains in place after being struck and is then struck again when the die comes down for a second time. The planchet has normally shifted or moved slightly in between the two strikes, resulting in the contours of the first image remaining vaguely visible, offset from the second image. On the odd occasion this creates a double effect of letters or numbers, which can change the appearance of the year, e.g. 15-662 instead of 15-62. This can lead to misunderstandings, with the uninitiated perhaps interpreting the date as 1566! Sometimes the coin will flip over in between strikes, so that the obverse image is struck onto what was the reverse and vice versa. This occurs most frequently in the smaller coins minted under William I of the Netherlands.

Medal alignment:

In general, the reverse die is rotated in minting. In other words, compared with the image on the obverse of the coin, it is turned through 180 degrees. This is not the case for badges or medals, when the image is oriented in the same direction on both sides. How to check this: hold the coin by its edge with the obverse facing you and with your thumb and index finger at ‘north/south’. Using your other hand, turn the coin over along the vertical axis . If the image on the reverse is now facing upright then we call this ‘medal alignment’. In the literature it is indicated by ↑↑. If the image is upside down, it is called ‘coin alignment’ and is indicated by ↑↓. Medal alignment is also called ‘crown alignment’ (kronenstand ) after the oldest types of cents (Centen) that were minted under William I. In the case of medal alignment, these coins show the crown above the W on the obverse and the crown above the coat of arms on the reverse in the same orientation. Very occasionally there are cases in which the reverse is rotated just 90º or less in comparison with the obverse.

Duit Zeeland 1797/96 (Lsch.112b)

20 Francs 1813 – LSch.171 (164)

On a few coins, it is possible to see faint traces of other numbers under the date. Rather than being a mint-made error or double strike, these coins are the result of an intentional alteration to the die. For that particular year, the mint has taken an existing die that was not yet worn out and simply changed the date in it, thus saving time and above all money by not having to produce a new die. The term ‘overdate’ implies that the new date has been struck over an older date, e.g. 1830 over 1820 (in brief: 1830/20) but this is actually not strictly true. If the date has been changed on the coin itself, this is of course no longer a case of overdate but rather a counterfeit.

Helaas heeft het benoemen van overslagen / jaartal-wijzigingen het effect gehad van beduidend hogere prijzen voor deze stukken. Het is daarmee zeer aantrekkelijk geworden om deze overslagen te ontdekken en te benoemen. In de eerste helft van de 19e eeuw vond de productie nog niet in stofvrije ruimtes plaats zodat een korreltje of stofdeeltje de slag kon beïnvloedden. Met name als er gerefereerd wordt aan jaartal-wijzigingen over niet bestaande jaartallen is het wel verstandig om hierbij enige terughoudend te tonen. Daarom zijn ook niet alle in de loop der tijden genoemde overslagen opgenomen in dit handboek.

Zie hiervoor als voorbeeld de 20 Francs 1813 over 1812 die m.i. onterecht wordt opgenomen in de NVMH almanak. (Zie toelichting bij de aanvullende informatie LSch.171).


Gouden Dukaat 1799, Lodewijk Napoleon (LSch.133a)

Hybrid strike:

There are cases in which coins are struck using the same die for both the obverse and the reverse, such as the Cent under William I. Sometimes two different dies are used for the obverse and reverse that do not actually belong together.

Gouden rijder 1799 (LSch.43)

Philippe Ferrari


Philippe Ferrari de La Renotière (11 January 1850 – 20 May 1917) was a renowned collector of stamps and coins. He was born in the luxurious Hôtel de Matignon in Paris (which currently serves as the official residence of the French prime minister), where he lived until two years before his death. As the son of very wealthy parents (the Duke and Duchess of Galliera), Ferrary inherited a sizeable fortune, which he spent on acquiring rare stamps and coins.

He was an impulsive buyer who was always on the lookout for extreme rarities. His apparent indifference to the price created a market for counterfeits and forgeries. These coins were made to order, but were never intended as legal tender. Because the coins were also produced by the KNM, I have included them in this database. Such coins gained the nickname ‘Ferrarities’ – a combination of ‘Ferrary’ and ‘rarities’. Over the years, this nickname has become the general term used to describe coins that were later minted by KNM but were never used as legal tender.

Examples of this can be found at Willem I and Wilhelmina, where pieces were made on behalf of J. Schulman (my great-grandfather) in 1905 by mint master van der Wall Bake.

Below you can view some unique documents from our family archive (click on the photos to enlarge):

  • The itemized invoice from mint master van der Wall Bake to Jacob Schulman.
  • The receipt of payment

Ferrary’s British numismatic collection was sold by Sotheby, Wilkinson & Hodge in London over a five-day period from 27-31 March 1922. The catalogue featured 710 lots and 15 Plates. [L1] Other sales of his collection, including French and ancient coins, were held in Paris. Some of his Dutch coins were auctioned off by the company Fa J. Schulman in Auction 153 in November 1925.

5 Gulden 1912 vals

zie voor vervalsingskenmerken
De Geuzenpenning 1968 (p27-35) van J. Evers.

Fakes and forgeries:

Coins showing certain years and designs are rare and therefore hard to find. As a result, these items are often very valuable, making them attractive for forgers. Although prostitution is commonly regarded as the oldest profession in the world, in reality counterfeiting is the oldest trade!

But what is the difference between a fake and a counterfeit?
In my view, a fake is a new ‘coin’ that has been produced by someone other than the authorised Mint with the intention of passing it off as a coin produced by the Mint. I use the word ‘counterfeit’ to describe an original coin that has been altered in some way.

Minted coins that have been cast by counterfeiters can generally be discerned from the real thing with the naked eye (e.g. visible imperfections) but it is often more difficult to detect an alteration to a date or mint mark. It can even make financial sense for a counterfeiter to set up a professional silversmith operation if there is enough money to be made. By the way, it is debatable whether it is wise to publish details of the tell-tale signs of counterfeits. They can be read by counterfeiters too, who then use that knowledge to perfect their fakes and forgeries.

2 ½ cent 1945 Netherlands Indies

Fantasy pieces:

Over the years, many fantasy pieces have been launched that look a lot like coins but are in fact medals. To the untrained eye these medals can sometimes look very much like the real thing, meaning that they are often incorrectly seen as restrikes of coins. Occasionally a fantasy piece is also slabbed, in which case it should be noted that slabbing is no fail-safe guarantee of authenticity.

2 ½ Gulden 1841 (LSch.382)


A galvano is a replica of coin that is produced by galvanisation (electrolysis). This process makes it relatively easy to apply precious metals to a surface layer, which means that it is an effective method for making accurate imitations of copper, silver or gold coins.

Museums have used this method to produce replicas for exhibition purposes (for security reasons) and for sale to collectors. Such copies are usually easy to discern from the original. A soldered joint is usually visible along the edge, for example, and it is not possible to add lettering or decoration around the edges using the method. When a galvano coin is dropped onto a marble slab, it usually makes a duller sound. Upon closer inspection, there is often a colour difference too.

 1 Franc 1814 (LSch.181)

Gebiffeerde stempel:

Al in 1813 waren uit Parijs stempels ontvangen met het jaartal 1814 maar toen de angst ontstond, dat ‘De Verbonden Mogendheden’ Frankrijk zouden binnenrukken kreeg de Munt te Utrecht opdracht deze stempels te bifferen. Bifferen is het onbruikbaar maken van een stempel, in dit geval met het doel te voorkomen dat deze stempels in de handen van de vijand zouden vallen. Dit heeft men dan ook werkelijk op 25 november 1813 gedaan.

Toch zijn met deze gebiffeerde stempels nog afslagen in lood van elke denominatie vervaardigd, die zich nu in de Nationale Numismatische Collectie, De Nederlandsche Bank bevinden.