There is likely a manufacturer's name on the back of the spoon. If there is look it up and see what years they were producing similar items. Otherwise it looks like a fairly common nickel silver spoon, in a style that was made for a long time, with little way to get any accurate date.
Well know for fact its silver, did test on it and said silver, plus it had green on it when found and silver has that kind of reaction, and theres nothing on spoon that says anything
Actually silver turns black with tarnish, brass, copper, and nickel silver turn green. It may be silver plated, but if it were sterling it would be so marked. You'll know when you find real silver, most of it comes out of the ground still shiny, or with very little corrosion. U.S. silver coins are 900 fine and sterling is 925 fine and I don't see silver coins being found that are green.
I know it's been awhile but you know the spoons like that are pretty cool finds ( if only worth their weight in brass)
and the Button deal IMO looks like Some Decorative Piece off Furniture or maybe a more modern button off a Coat or something.
Just Curious
Where you hunting at.?
Davers