This is a 'Silver Strike' - the $20.00 'prize' in special slot machines. There were several designs that were considered collectible items. They could be cashed in for $20.00. The coins are in a plastic case to protect them. It became a service nightmare, as the cases chipped, bouncing around in the machines... the fragments jammed up the works of the machines. There were usually 3 or 4 designs (keep playing until you win them all!), and designs were changed periodically, keeping collectors coming back.
These coins are .999 fine silver.
This tiken features "HR" logo in gold and the outer circle in silver. On the back is the mint mark "S" for Sunshine Mint.