I posted a coin in a thread a few months back that Doug Smith astutely asked if it was a fourree. I didn't have access to the coin until today to weigh and look it over, and I'm still puzzled. It's weight and axis are right in the sweet spot: 1.78g, 4h. There are these areas on the lion, around the facing rim, on Fulvia's ear and other areas that look in this picture like the silver coating of a fourree that has worn through. I'm not positive (are any of us positive of anything with ancients?), but I don't think it's a fourree. It does look like a layer of metal has been worn through and exposing a secondary layer which is now covered with a black toning or something but it doesn't look like copper/bronze. It's not happening haphazardly; it's on high points where there would be the most wear. So this is where it gets even more weird. I did a bit of research across some of the major European museums and I see this is not unique. Here are some examples: American Numismatic Society. Check out the lion's mane, front paw, front of the exergue line, maybe even the rim. Berlin: The body of the lion, feet and IMP. Anyone have any ideas what this is? Looking CoinArchives, there are other examples but I'm assuming Berlin and the ANS know their way around fourrees better than the average auction house.
Do coins of this period show signs of surface enrichment? I could see the signs explained by that but I was not aware that it was done here. For those not aware of the concept, the idea is that a coin blank of silver copper alloy could be soaked in an acid that would leech out some of the copper from the surface leaving a honeycomb of pure silver. When the blank was heated and struck by the dies the honeycomb would be mashed into a surface of silver of higher quality than that of the center part of the coin. I really would like a book on technical matters as shown on ancient coins but there is much less interest in this part of the hobby than in types and dates. None of these coins show seams like at least some fourrees of the period do so I agree that the coin probably is not fourree. The Berlin coin looks exactly like what I would expect from a well worn surface enriched coin but I am a beginner in this so may be missing the obvious answer. Do denarii of the same period/issues show similar artifacts? The only ones I have are fourrees (without question!). I really believe that people absolutely certain of their answers rarely fully understood the question. All of our studies need to be footnoted with the fact that new data might change the accepted facts. I know I am not keeping up with many things. In my generation there were nine planets and dentists insisted you use hard toothbrushes. I just found an interesting photo fig. 1.1 on https://books.google.com/books?id=D...epage&q=surface enriched silver coins&f=false but it is too late tonight for me to digest this. I had once considered buying this book but never did. Who has it and would give a review?
Doug - Wow. That is an excellent observation! I was not aware that this actually done purpose as I thought this phenomenon happened naturally...somehow. I'm pretty slow unless there are cartoons, crayons and Count Chocula involved. This is something I will need to research. What you say makes complete sense and I think is quite probably the answer. I just wonder if it was done on purpose or a byproduct of some sort of smelting technique used in Lugdunum at that time.
I would like such a book as well. Unfortunately, the best info on the ancient minting process I've seen comes from books on counterfeit detection, so it's more of a secondary topic in that context.
Paul is 100% right on this one! Studying technical points makes some fakes stand out as obvious and also makes some coins seem more likely to be good just because most fakers don't go so far as to copy little details unique to one particular issue. I find technical studies fun but will allow those interested in avoiding fakes (most of us) to buy the book, too. The question is who will write it???
Kevin Butcher and Matthew Ponting's The Metallurgy of Roman Silver Coinage: From the Reform of Nero to the Reform of Trajan goes into great detail about the minting process. It's really worth the steep price tag. The practice of silver enrichment is of course covered.
