I occasionally clean a coin and realize that there was, or sometimes still is, some kind of metallic coating. I presume it was often a silver alloy. Sometimes the coating manifests itself as flat earthy clumps that sparkle underneath, sometimes black flakes, sometimes silvery surfaces, sometimes light grey or orange-tinged material. A couple of coins have suffered because of this, so my policy is that, as soon as I detect a different construction than normal, I stop cleaning. Typically, further cleaning makes it look terrible and the coating is diminished. I will hold those coins for fun and maybe in future learn how to clean up each type. I'll try to attach a picture of a "camp gate" reverse that exhibits silvery portions.
Silver washes were common on late 3rd-4th century bronzes. The silver was really just for show and rubbed off quickly with use since there was so little of it on the coin. Occasionally a coin that still has its full silvering turns up, but most bronzes from this era only have faint traces left (if any). And even that tends to look more like toning or patina than silver.
Silvering started during the time of Gallienus and lasted about 100 years with the exception of a few coins that actually were just base metal and were not coated (Post Reform Radiates of Diocletian come to mind). The silvering indicated that the alloy of the coin itself was intended to contain silver but just no enough that the coin looked silver without the wash. These usually range from the XXI issues of Aurelian through Diocletian era at 4.77% down to some in the 1% range. These alloys do not weather or clean exactly like copper and we see a lot of rough coins that just won't clean up to look right. We also get a few that remind us of what they looked like when new.
Once as I was cleaning a Roman coin I realized some of the surface had a gold colored material still sticking to some areas. I did not clean any further and still have it somewhere (I will have to find it to get a pic). But has anyone ever heard of gold plated coins from that era? Could it possibly be a plated counterfeit?
To Rdwarrior, there are gold forgeries but usually not with copper cores. Copper is too light, most gold forgeries would be with lead or silver cores to give weight. Trying to pass a gold forgery is hard enough, but then for it to weigh so little is a dead giveaway. To the OP, yeah that type of silvering is the hardest problem you will find trying to clean coins. If you can save it it is always best, but sometimes it is so far gone the coin will be best preserved by removing it so you can clean the underlying copper well. Each case is unique really, and always a difficult decision unfortunately.
Gold plated copper cores are not all that uncommon especially in the Byzantine period. Top is Basil II and Constantine VIII; bottom is Basil I and Constantine. Also note that some silver coatings tone with a gold like color so it is possible to find a gold looking plated coin with no gold at all.
They look like copper to me but I have not dug in to be certain. That will require a trip to the bank to investigate.
Those are interesting, thank you for sharing them. I own a greek gold fourree core but it is oxidized white and yellowish leading me to believe it is a lead alloy. I would wonder how they passed a gold plated copper coin since it would be dramatically lighter than gold, while lead and or silver would be more passable I would think. I would love to hear what the specific gravity of them would be, if it wouldn't hurt the coin to test.
Dougsmit - what is that first Constantinus camp gate coin you posted a shot of? What a beautiful portrait. It could almost pass as an argenteus with all that silvering.... almost.
The Constantine I is from Heraclea mint RIC 16 p.544. I find it interesting that I have seen more coins of this issue with remaining silver so it seems that there was something done differently there that made the plating better. You will find certain issues are rarely found with remaining silver while others are more often silvered. Whether this is more than random I do not know. Of the coins in my collection, the only other well silvered piece is this Licinius II RIC 19 p.545 (same issue). It is hard to visualize all those late coins looking like this when they were new.
That is interesting. I wonder what it is that makes that specific issue's silvering stand the test of time better than others. Beautiful coins mate... I sure do like that Heraclea Constantine I.... I still don't have any coins of Constantine I ... I might keep my eyes open for that specific issue, if I ever come across one. I really like the bust. He is holding a sceptre in the one hand, and is that an olive or palm branch in the other? It's hard for me to tell. I have not spent very much time learning about Roman coins much later than AD 253, but I am starting to find some issues from the early 4th century that I quite fancy.
Great coins! yeah I'd liek to find a nice one with most silvering still on it too. Heres the only example I have atm.
The thing that always worried me about the 'silvered' coins from this time period, is that it seems like it would be relatively easy for someone to put a thin layer of silver onto a coin that has lost all its silvering. But I would assume collectors of these types would be able to tell the difference. Cool coin randy, Constantine I? I always liked the wreath reverses.
Usually the silver is not complete since it was not a layer of silver put onto the coin. I believe the entire planchet had a low silver content, and then they soaked them in sea water to remove the copper from the surface. Then the die striking melted the surface silver and made it look much more silver than it was. When you hold them in hand you can see the silver is part of the metal. When they are in bad shape the silver can come off like silver plate of leaf, but if the coin was in bad shape any collector should realize it should not have its silvering intact. Best I can describe it I guess. Others might be able to describe it better.
