There has been some discussion on the ancient Coin Talk forum and on the main forum itself about conservation as opposed to cleaning a coin and the part that a third party plays in establishing a grade for conserved or cleaned coins. I have some what-ifs to propose. What if I took the coin below which has already been graded and encapsulated by NGC but shows some heavy horn silver deposits, removed it from the capsule, treated it with sodium thiosulphate to remove the silver chloride, and sent it back to NGC for regrading and reencapsulation? SICILY. Leontini. AR Tetradrachm (17.23 gms), ca. 476-466 B.C. NGC AU, Strike: 5/5 Surface: 3/5. HGC-2, 660; SNG ANS-202-3. Obverse: Charioteer, holding kentron and reins, driving quadriga right; above, crowning Nike flying right; Reverse: Head of roaring lion right; four barley grains around. Well centered and quite deeply toned, though some minor roughness is noted upon the reverse. Would the coin come back to me with a notation that it had been cleaned or conserved or neither? What if the coin was raw and had not been slabbed and graded, and I sent it in to be conserved and graded and encapsulated? What note or comment would it receive? What is the difference if I conserve a coin or NCS does, and who determines if my conservation method did basically what NCS does and shows no signs of having harmed the coin? I guess NGC would decide that. Would NGC be able to determine that I had removed silver chloride from a coin without seeing the coin before the treatment? Actually, I have treated a coin for horn silver with sodium thiosulphate and sent it to NGC where it was graded and encapsulated with no notation. But what would happen if I removed the above coin from the slab, treated it, and resubmitted the coin for grading? That's a what-if to which I would like to know the answer.
Sodium thiosulfate is a pretty market acceptable treatment, I believe. I would leave it in some acidic paper for a month or two to get some mild tone back and the TPG wouldn’t think twice
NGC Ancients doesn't regard "cleaning" in the same way as the mainstream NGC service. Were the op to be properly cleaned, I suspect the "surfaces" rating might improve. [edit] ... assuming further cleaning does not reveal less attractive surfaces below the hornsilver. One has to consider the possibility that previous cleaning stopped where it did for good reason.
Most ancient coins have been cleaned at one time or another, so cleaning really isn’t an issue with ancients as long as it’s well done. If the surfaces were improved the surface grade would go up. Most people unfortunately tend to over clean their coins and bright, brushed and unnatural looking cleaning will get a lower surface grade. I don’t recall this coin off hand as to why it was a 3 surface. If there are underlying scratches or surface porosity, cleaning won’t improve the grade because those issues will still be present, in fact cleaning might lower the grade if those issues became more obvious and distracting. It doesn’t matter if NCS conserves the coin or you do. We just grade the coin as it’s presented to us. If we had thought that having NCS conserve the coin would have improved the grade, we would have recommended it. Barry Murphy
