PAT. APPLD. stamp on both the base plate, and the back of the gear cover, and the single line Kluson Deluxe stamp in the middle of the gear cover.
This, the first of 3 styles of Kluson Tuners seen on Black Guard Telecasters. were used from the introduction in late '50 until about mid '51, when we begin to see the closed shell "No LIne" tuners.