Vintage Seiko dive straps
The GL-831 strap came on the Seiko 6306/6309 Turtle diver, the H558 “Arnie” ani-digi diver, and even some references of the famed 7c43 and 7548 quartz divers (among others).
These watches were rugged, a professional divers CHEAP alternative for everyday use instead of his priced Rolex Sub, and meant to be used in salt water, which is likely why most of the surviving original straps are prone to deterioration.