27.6mm; 11.0gr I used 'large' in the title with awareness that there are 'larger' cents out there. It looks in places like some plating or other surface treatment (yellow) has worn away, leaving the red/brown of copper. Is this an important coin?
No, that's a perfectly normal and worn large cent. If the coin is unusual, its because it doesn't appear messed with, like 95+% of large cents.
Actually it does appear messed with. It appears to have a layer of lacquer on it and it's wearing off in spots.
I think conder is correct. Looks like lacquer on the surfaces that is now falling off. Still a decent little large cent.
If that is lacquer (even though it's been there for some while) it ought, IMHO, to be allowed to dissolve in an appropriate solvent...chosen to minimize unwelcome alteration to the coin surface. I've started a new thread to state my opinions about 'cleaning', and would like to have a meaty discussion about this taboo.
