Need much better pics to try to confirm or deny. Pic needs to be head on, in focus, and everything but the coin cropped out. an easy way to get the head on shot of the coin is to rest your phone on a can of coke or can of soup or anything about that size. I use the three second timer on my photo app and take the pic. From there to photo editing to crop around the coin.
Should should I try to peel it off it is raised but it looks it's silver though you know shiny like zinc
Try a bath in distilled water first then some gentle picking with a wooden toothpick…. If it’s still there, and it most likely still will be, you can try an acetone bath but read up on acetone first. It’s not the nicest stuff out there. If you do try acetone, make sure it’s pure. The nail polish remover has other stuff mixed in.
Try the distilled water…. It may soften the residue and it’s not dangerous. From your pics paddy has it diagnosed correctly as adhesive.
That's not a Cud. A cud is a piece that broke off the die so when the die strikes the blank planchet the metal from the planchet flows into the void. There wouldn't be any part of the design besides a raised blob of metal. Here's are examples of a cuds
I can’t see anything in that photo. A shattered die has numerous die cracks all meeting at a central point and reading out to the rim of the coin. A cud must touch the rim as a piece of the die broke away. From what I can see I agree with dried adhesive.
It's dried epoxy on the coin. But it does resemble the coins my great grandma used to attach to the inside of my b-day card with clear tape when I was a little kid in the mid to late 70s. After a few years the clear tape would become brittle, breaking off and leaving tape and adhesive on the coin.
