Opening old .wallet files

I've found some old .wallet files that I don't recognize and I don't know how to open them. They have names like, for example, bisq_BTC.wallet. The odds are that they're worthless (I'm just not that lucky) but I'd like to find out how to open them just in case I had some BTC or other coins from back when they weren't worth much. Anyone have any idea.how to open dot wallet files? Note that they're not wallet.dat but rather *.wallet.

Hmm. It's telling me that I need 500 Characters to post. Why is that?