mounts 51 and 52? (is that how you name them?)
In USN practice, yes, this is how mounts are numbered. The first digit is the caliber in inches, the second digit counts upward from the bow (if there are beam mounts, odd numbers starboard, even numbers port).
For main battery turrets on battleships (and maybe cruisers?), I think they're just turret 1, turret 2, turret 3, but I'm less sure on this.