Something that is very valuable and is expensive.
nonvaluable
Materialist.....maybe? edit: I was thinking more of love for nonliving-nonvaluable things. Like, plants or houses or lamps. Random nonliving things Plants are living things....unless you're a vegan with no compassion for plant life. I found the word objectum-sexual for people in love with inanimate things. Hopefully that is closer to what you had in mind. If not, we may have to invent a new word.
Are you sure it is tarnished and not an off-metal strike? Should be able to tell by weight. And if it's not valuable, spend it and let someone else worry about it. == Brasso or another metal polish will do the trick. You could also just use some fine steel wool and do it "dry" or make a slurry of scouring powder and a bit of water to form that slurry or a paste. Look the coin over first before taking it to the cleaners to be sure it's a "regular" coin and not a "valuable" one.