It is a different color only because it has been handled for 82 years. Just the grime left by countless hands. No mint mark simply means the nickel was struck in Philadelphia. Myself, I would give this crusty old veteran a flip and hang on to it for posterity.
I'd definitely keep it. I have no idea why people are saying spend it. The color is environmental toning, and has no added value. The reverse isn't supposed to have a mintmark as it was minted in Philadelphia. But I would still keep the coin as they are a fun thing to find and it's almost 100 years old.
Hi Kennyeva and welcome to Coin Talk!! Well based on the replies, I guess you can keep it or spend it. Kinda like where you were when you started this thread!!! HUH! Bottom line is it's not a bad old Jefferson and if you like it you should keep it. It's your collection so it should contain coins you like!!! If you don't like it that much then you won't be losing a lot of money to spend it!!
Make no mistake, i keep every nickel i find 1945 or earlier, every single one. I have a ziploc bag of 1939s that I've found at work. My point was, if there's no real vested interest in the coin, or the date, then spend it. It may just end up in my ziploc bag, eventually. Or keep it, like i do, for no reason in particular, other than i think it's cool.