Rectangular buckles were fairly
rare in the
Roman era. In central Europe they are generally descended from
German proto-types (used by the Wielbark and Przeworsk cultures).
So if
Roman it is likely a regional variant.
The large loop on the end looks like what you find on a harness strap end to attach to a harness junction ring.
My guess is therefore that it is a
horse harness buckle used to tighten a girth strap.
SC
