When appearing on 2-piece belt buckles, the US Navy's emblem always included stars, and an encircling rope border. Because your buckle has neither stars nor a rope border, I think it is a foreign Navy buckle ...specifically, a European Continent nation (excluding Britain). The British Navy emblem is similar to your buckle's emblem but tends to includes a crown atop the anchor. The Navy emblems of France and Germany are a "simple" anchor-with-rope, so your Navy buckle may be from one of those countries. Here's a photo of a French Navy button from the second half of the 1800s-to-early 1900s.
