A small roller buckle for 13mm (½in) straps. It's solid brass rather than brass plated, so there's no plating to wear through and it can be polished back if it dulls.
The roller sits on the front bar, so the strap end slides over it without scuffing when you pull it tight. The pin hinges on the back bar, and the strap fastens through a punched hole. Suits watch straps, small bag and purse straps, spur straps, and cat or small dog collars. You'll want a keeper for the loose end.
