It's possible they could be satin finish but it just seems much more likely u got an old box of unc regular finish coins that have toned over the years than some large dealer dumping that many nickels from mint sets. The toning can sometimes be a little misleading on some coins. But its a cool find and they should have some numis value either way. I'd have them appraised by a coin expert to confirm before u try to sell so u know for sure what they are and have a better idea of value. GL
I was just thinking about Maverick finding a whole box of clad half proofs recently. Its possible some large dealer like that guy on HSN has been busting open thousands of mint sets and proof sets lately - maybe to put together a large quantity of Kennedy half dollar sets to sell later this year to try and capitalize on the hype he will be trying to create about the 50th anniversary of the JFK half dollar or something.