I have a a strange buckle which I bought in an army surplus shop. Its brass the buckle can be opened as in the picture. When I bought it there was a piece of leather strap about 8 - 12 inches attached with holes for fitting to another buckle. Clearly its some sort of quick release but I can't guess for what. By the nature of the buckle it has to be kept under tension or it will just fall open and undo. I wear it as a belt buckle so it is kept under tension. If any one can id it I'd be grateful.