Kennedy Halves Silver And Gold

Just for starters I don't really know what I'm talking about when it come to coins, so if these are stupid questions or common knowledge then sorry! I ordered 3 boxes of halves from my bank hoping to pull out some silver(I just look at the edges). I had ordered 1 box before these 3 and got skunked so I really didn't expect much. First couple rolls opened and I come across one bright white/silver edge sticking out like a sore thumb in the roll. So I pull out the coin and it's a 1974 no mint mark. This thing was shining and looked almost uncirculated. So I didnt really know what it was because I just look for 1970 and under silver coins. I set it aside and as I start back through the rolls I continue to stumble upon these bright white/silver edged, shining AU coins that are all over 1970. What have I found? Are these coins silver? Are these proofs? Here are the dates: 2 1976 bicentennials no mint mark, 2 1974 no mint mark, 1 1971 no mint mark, 1 1971 d, 1 1974 d, 1 1972 no mint mark, 1 1979 no mint mark, 1 1989 p and 1 1997 p. Let me know if you can help based on the information I've provided. My second question was about the gold plated Kennedy halves. I also pulled 12 of those mostly out of the first box and these too have shining surfaces and look AU. Could these gold coins have once been proofs and someone gold plated them? Thanks guys!