@TypeCoin971793 mentioned in another thread https://www.cointalk.com/threads/go...-fall-of-wang-mang.315047/page-2#post-3362527 something he called 'patina transfer', a term I have never heard before but understand. I thought it a topic worthy of a separate thread. I've actually never heard or read anyone trying to describe it but I suppose a better term might be 'patina pattern'. For European coins it is rare to encounter as most coins are immediately cleaned. But with Asian coins many come to market uncleaned and examples can be found a bit more easily. Patterns form in the patina of a coin when an object lies against the surface of the coin and over time the patina forms around said object leaving behind a mirror image. Sometimes the pattern is from another coin (and this is common for Chinese coins where they are buried in neat stacks). I came across the coin below this weekend which shows a nice textile pattern. Post any you might have:
Here are a couple other Chinese coins that have patina transfer, in which the patina between coins is literally transferred from one coin to the other when the coins are separated after being discovered in a hoard. This is an extremely good indicator of authenticity as it means that the coins were in the ground long enough to become fused. Ming Hua with some character outlines on the reverse. Yuan round coin with a clear patina transfer to another Yuan coin from the reverse. Patina was tranferred to this coin on the obverse, meaning this coin was stuck between two others of a similar type. I have seen many with this patina style, so I believe this coin is from a hoard of of over 1000 Yuan coins discovered in the 1980’s. Here are three examples of spades which have patterns in the patina indicating that these spades were in direct contact with other spades in the ground. This is a “patina pattern” which @Ken Dorney describes since the patina is not transferred from one coin or another. Again, this is a fairly good sign of authenticity, but I have seen multiple fakes which try to mimic this pattern.
I don't really collect Chinese coins (which means I only have a couple hundred). I can't say I have exactly what you are describing here but am quite fond of this extremely rare coin from the year of the Giraffe. Those who do not look for shapes in clouds my call this a Hartill 18.40 Zheng Long yuan bao 1158-1161 AD but they know not. I wonder if the emperor ever had seen a giraffe.
Not a joke: A comprehensive collection of cast Chinese coins would be several times as large as similar coverage of Romans. They made them by the billions. The simplified reference Cast Chinese Coins by Hartill uses a rarity scale with 10 to 16 defined as varied degrees of 'common'. I did not count them but there must be a thousand 'common' types listed. Two hundred is nothing.
Can confirm. They are so common, I sometimes have 200 of a single type in my collection. I bought these to look through hoards to see what was in circulation at the times these were lost. I’ve since sold about half of them.
I've taken a bit of time to think about this new term 'patina transfer' and I just cant get behind it. Patina does not 'transfer' it simply develops according to its environment. Patina from one coin cannot transfer to another though it could be shared.
What I am referring to specifically is when two coins have fused patina, and breaking them apart causes the patina from one to be ripped completely off the surface of the coin and stay attached to the other coin. My Yuan coin shows this the best. Maybe “transfer” is not the best word since, as you said, it is technically “shared”. But what I am thinking is that the patina which developed on the the surface of one coin becomes part of the encrustation of the other coin when the two are separated, and this is where I get the idea of a “transfer”.
The 2018 American Journal of Numismatics has a long article by Lyce Jankowski, "History of the Chinese Collection," which explains how the ANS came to have one of the most important collections of Chinese coins in the world by acquiring major private collections, several before 1920. If you are interested in Chinese coins, you will find the article very interesting.
Two of my coins came to mind when I read this thread... neither are nice coins but both have patterns from patina that was formed between these coins and others that were buried with them. On this Constantine, you can see the arching outline of the coin that was above or below it. If I had the guts and skills to remove some of the thick patina, it would be a pretty nice coin. On this cruddy Diocletian from a group lot, you can see the impressions from the legend of a coin that was pressed against it. I've tried to decipher the letters but...
This second coin is a great example of the patina all the way down to a coin’s surface being stripped and becoming part of the encrustation of another coin. This is what I refer to when I say “patina transfer”.
