Keep if you like it. Soak it in some pure acetone for a few hours per side and see if it cleans up. Floating roof cents are pretty common on 69 & 70 cents though. After soaking, rinse and dry. Put it in a 2X2 cardboard holder and label it "Floating Roof" -
"I have enough money to last me the rest of my life, unless I have to buy something."
Working on a Dansco 8166 Kennedy half album. 131pcs ,of 160 total, so far