If it is copper embedded there is one possibility that this is a mint error. A lamination of the planchet struck before this coin coming loose and dropping onto the anvil die surface before the next planchet was fed, assuming the obv. die is the anvil.
It is uncommon and I am not to familiar with this type of error but I remember seeing a coin with a piece of wire embedded, it is called retained struck through. Here is a link that might help: http://www.error-ref.com/retained-struck-through-staple/
Ok. I got some acetone and applied with a Q-tip for several minutes. I have attached 3 images of Before, During and After. The area in question discolored to a grey-green. I tried to chip it off but it does not flake off. Any thoughts?
That's not acetone. That's nail polish remover. It's made from acetone but you don't use nail polish remover on coins as it will destroy them. The acetone you need is an industrial grade. Luckily the Cent in question is only worth face value. That's just glue on it as previously stated. Heat it in a small pan of hot water and you can probably peel it off.
45 year old Mystery Solved. The acetone did work....it flaked off a piece of glue! Thanks all who shared.
Welcome to CT Todd. I'm glad you were able to solve your mystery. For the future, the reason for not using finger nail polish remover is because oils and other things are added to the acetone to help keep the cuticles from being damaged. This could damage the surface of the coin. Acetone you buy at the hardware store should be labeled, 100% or Pure acetone. For any other questions about coins, or currency, don't hesitate to post on Coin Talk.
Pure acetone is just that. Pure acetone. Nail polish remover (did you really find that in a hardware store?) contains fragrance (and maybe bitters). Pure acetone- good for coins though I prefer xylene. Nail polish remover (with additives) - not recommend for use on coins.
A tip of the Hatlo Hat to you for being honest enough to respond. Do you collect any other stuff? You will get good advice here (along with some 8th grade attitude).
As noted by your fellow enthusiasts, pure acetone. It should be the first and only ingredient. Good luck on the hunt!
Now don't you feel bad for questioning the experts! Remember, you came here asking the question. Welcome!
But when that happens you also get VERY strong clash marks in the fields. The devices are incuse in the dies so for the devices of one die to show on the other die they have to cut into the fields of the die to that depth as well.