World Coin Clinic: What is a Boardwalk Flan?

By Richard Giedroyc

What percentage of ancient coins being sold are from older collections and how many of them are from recent discoveries?

There are no hard statistics on this, however, it appears that prior to 1975 it is likely about 70 percent of the available ancient coins were likely being resold from older collections. This changed around 1975 due to the use of metal detectors. From this point forward, about 30 percent were from existing collections, while about 70 percent were from fresh finds. Since there isn’t an endless supply of coins to be found, the available fresh finds have dropped significantly since about 2010.

Do we know the contemporary value of ancient Roman coins?

The purchasing value of a coin and wages has always been a moving target based on where someone resides and when that person lived there. Wages vary across the United States today, just as they did throughout the ancient Roman Empire. Some interesting reading on the subject appears in Volume 2, Page 21 of David Vagi’s Coinageand History of the Roman Empire and in David Hendin’s Guide to Biblical Coins. There are many additional sources.

What is a boardwalk flan?

Some ancient coins were struck on oversized and likely very thin planchets that allow the image to be encircled by an oversized blank edge resembling a boardwalk. I say ‘likely thin planchet’ because the coinage blanks were weighed for accuracy but unlike modern coins, little consideration was given to the diameter.

What can you tell me about using Renaissance wax to protect my coins?

Renaissance wax can protect coins from the environment but in most situations, it simply isn’t going to be necessary. This is a special conservation wax designed to protect coins in a humid environment or bronze coins that have shown signs of ‘bronze disease.’

What is ‘bronze disease?’

Patina is a hard green or brown coating often encountered on ancient and medieval bronze coins due to corrosion. The patina will seal the surfaces. When this coating is attacked by hydrochloric acid and forms tin-chloride and copper, the coin is actually beginning to deteriorate due to this chemical reaction.

Is there a way to determine mintage figures for ancient and medieval coins?

There is no fool-proof formula through which mintage figures for these coins can be determined. However, once the number of obverse and reverse dies used for a specific coin type has been determined, estimates can be made based on what is anticipated to have been the life of each die.