How to remove glue / adhesive residue from metal?

Have you tried WD-40 (the miracle chemical?)

https://wd40.co.uk/

Acetone, petrol, dichloromethane are all the same class of chemical. I suspect your "glue remover" is more of the same (ethanol + C12-C14 alkanes).  If they haven't worked so far, they're not going to do it.  

First try (soap &) Water!!! 

If that doesn't work, try an alcohol (e.g. beer or wine cheapest) 

Or surgical spirit, or turpentine. 

It that doesn't work , try Acetone(Propanone) , which is a very good solvent for organic glues and adhesives. 

None of these solvents will react with the metal. 

However,  you can try a mineral (Sulphuric/Hydrochloric/Nitric)acid, or alkali, but be careful, they can dissolve the metal, and  'burn' your hands. 

Hi Robert. Residue, not sure, Will leave it in acetone for a few days and see

Soaking in acetone for a few days should remove any type of glue residue; don't expect it to work instantly.

Are you sure it is residue?

The coin metal may well have oxidised or tarnished more over time where it was not sealed from air by the paint/glue, so the mark may actually be a cleaner area.

one of those chemicals should work, but you have to rub gently with a soft cloth. Just soaking won't work. goof-off would be the first I'd try.