A late Roman 'Protrusion Style' buckle (see References below). The frame (now slightly distorted) is open and has incurved terminals with outward-projecting hinge-lugs for attachment to the plate. Decoration consists of mouldings on the periphery of the frame, and punched dots on the front face. The mouldings are in the form of two opposed upturned crescents on the outer edge. These are, in fact, very devolved versions of birds, other examples of which are far more naturalistic. The dots are punched in a single medial line around the entire front face of the frame.
See also UKDFD 3940.