there were three Silver Club - Sparks with different owners. Karl's Silver Club was open from 01/01/1968 until 1989 when new owners moved in (Stevens, et al.).

If you are looking to date your match covers on ebay the front strike was probably before Karl's (1968) and the back strike was after 1973 and before 1989.

On a side note the Mint Club match cover on ebay, does it have any printing on the inside? The one I have doesn't have a manumark and is blank inside. It's unusual for a match cover not to have a manumark. All it says is "MADE IN U.S.A." similar to yours.

Also, double check your Beef 'n Grog Lounge & Restaurant ebay auction.