[BCA]

Your pintle is very similar to a pintle that I have also been unable to identify. Mine are stamped B2536 and I believe this is a British number. There are also"&" stamping: perhaps a variety of proof mark. The spacing is 2-5/8" for the gun. The pintle shaft is that same as is seen on American gun pintle sand tripod mounts. Mine were packaged in 1950 and the part number was prefixed LV? Partially obscured.