I agree with Charlie P. It's definitely from a US Army 2-piece buckle for web-belt.
As to its time-period, I'd say approximately mid-20th-century. I used an army web-belt with that exact type of buckle back when I started relic-hunting in the early 1970s. Bought it at an army-surplus store. I believe mine was Vietnam-war surplus, but it might have been Korean-war surplus.