It has luster. That's just sitting under the toning. For a buck over silver, that's a nice buy. Problem-free, plausibly MS, 1949-S, let me put it this way, you could have done a lot worse.
Don't even think of silver value, that one has coin value. I think you got a great deal. Ben looking for a 1949-S myself.
The OP's coin IS a 49-S paddy! I think for a dollar over melt, you did great. This series really only has demand in MS in my experience, and circulated coins regardless of key date or not typically draw little to no attention.
It is a nice buy at $6.50. I would value this 49-S at about $10. It may grade as high as AU but the eye appeal will lower the value.
As nice as that OP coin looks at the price paid I would be very tempted to pick up a good used Dansco and fill it with similar examples at or near the price paid. Well played I say.
It is usually due to contaminants in the environment. It could be from contact with whatever it was stored in, or oils left from someone's hand when they touched it (the coin appears to have been handled quite a bit over its life, and probably grades a high AU). I sometimes call them "sneeze marks" - imagine someone sneezing in the vicinity of a coin, and all the little droplets land on a coin and start corroding it (not necessarily saying that's what happened with this one, but it sorta looks like that). Sometimes it can be removed, sometimes it can't.