This is a silver-tone Omega buckle on a NOS JB Champion 3/4 or 19mm tapered ostrich leg watch band that has a single chunky keeper and a max length of 6 and 5/8 inches when buckled. The buckle is signed only with "Omega" on the back, from what I  understand this was made between the 1940's-1960's for the US market. It is approx 15.3 wide across the exterior  with a 13mm interior. I believe it is authentic, I don't see any obvious indication that is a knock-off but I am not an expert so please see the pics and if necessary request additional pics.

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