Keyhole Bar
13 Fremont St
Las Vegas
1949-1955
No gaming that I'm aware of, but it was located in a corner of the Sal Sagev/Golden Gate. If you look closely, you can see that the doorway is shaped like a keyhole...

Here's the page on Over50Vegas https://over50vegas.themogh.org/13_Fremont_Keyhole_Lucky_13.html