York PA Medallions Info

Usually these medallions, if silver, will be marked as silver somewhere on the coin. Check the edge of the coin to see if there are any engravings.

The US Capitol Historical Society (USCHS) medals you've posted are from the first year of a 13-year medal program (1978-1991) issued by the USCHS. In addition to silver and bronze, the medal was also struck in gold.

They were authorized by an Act of Congress; the 1978 medals were struck at the US Mint. Subsequent medals in the series were struck by the Medallic Art Company (MACO).

Regarding your other York medals...

I'm not familiar with them, but they do appear to be silver. Examine both sides of each medal plus its edge to see if you can locate a stylized "FM" anywhere. If you do, that will tell you the medal was struck by the Franklin Mint and most likely sterling silver (i.e., 0.925 fine).

In any case, I would take them out of the foam rubber cases - the foam is notorious for permanently marking coins/medals placed on it and stored for a length of time.

Regarding values, the US Mint medals do have a collector following and can be sold for a premium beyond melt value; if I were selling the USCHS silver medal, for example, I would start an ebay auction listing at $40-$45. IMO, the others are a bit more generic and would likely need to be priced at $30 or less to open in order to attract attention.