The commonest metal-detecting find after coins — and surprisingly datable.
Buckles fasten belts, shoes, spurs, and harness, and their shapes follow fashion closely enough to date well. Roman buckles are often robust D-shapes, sometimes with military belt plates; medieval examples run from plain iron D-buckles to fine double-looped ('spectacle') forms; post-medieval shoe buckles are broad, decorative, and often silvered or tinned copper alloy.
Look at the frame shape (D, oval, double-loop, rectangular), whether a buckle plate survives, and how the pin (the 'tongue') was hinged. Decoration helps: knops on medieval frames, engraved post-medieval faces, and traces of gilding or tinning all narrow the window.
Buckles are honest workhorse finds — most are common types, which is precisely what makes them good dating evidence for a site. Record the frame width across the pin, the metal, and any plating traces, and match the outline against published typologies before assigning a century.
Identifying harness and horse fittings