Anyone have a guess as to what caused the damage on the surface of this coin? My thought is that it was covered in AgCl/horn silver at one time and was treated with sodium thiosulphate to remove it. There have been several discussions here on CT about this treatment. I have also seen some other coins offered in auctions that mentioned in their descriptions some damage from horn silver. Is it possible this coin was so thoroughly covered in horn silver that when it was treated, a large part of the silver was removed because it was in combination with the AgCl? I would be interested in hearing from some of you who have used sodium thiosulphate in treating horn silver as to whether you have had damage like this as a result. If this is not the cause of the coin's damage, what do you think it is?
My "guess" is that the surface layer became crystallized and it flaked off. I have not seen such sharp delineations between the remaining surface layer and the exposed under-metal caused by removing horn silver.
You could be right Pete. Could it be lamination of the flan at work too? It could be all three at once. John
