What does the hologram side of the coin look like when toned and is it heat or electrical toning?
"Chemical" toning and the holograms were applied after the toning process. On most coins there was no toning on the reverse side of the coin, which was just a side effect of how I toned the coins.
Thanks for the information, I wasn't thinking chemical as I thought the holograms were still applied but that makes sense. I have experience with heat toning but it depends on the contact metal and temperature control to get a clean appearance.
The coins' composition is copper alloy (85% copper), so it is highly reactive to even the slightest atmospheric changes. There wasn't any direct contact with the chemical (sulfur).