Here is the info on my guns. All serial numbers have been rounded to the nearest 500. No guns have the FN marking.
1. 3700. Has gold inlaid safety. Serial number ends with "P", marked "U" and "O" inside trigger guard. The "O" is by the front trigger although it currently fires the lower barrel. This may have been changed. This is a Twin Single gun and the triggers will interchange.
2. 7400. Pigeon Grade. No Gold,has "U" and "O" on trigger guard even though this is an early style SST gun.
3. 8600. All no. Twin Single trigger gun
4 9100. Twin singl trigger, no gold. This is receiver with triggers only and I do not have trigger guard.
5. 950. Double triggers. All no. Early monobloc gun with stepped rib, engraved "Superposed" on barrel.
I had never noticed the O and U inside the trigger guard on these guns. I would really appreciate more information on what you find, particularly on the "P" serial number I asked Glen at Browning about it and he said he did not know. The gun has imp cyl/full chokes in 30" barrels and I wondered if it was for live pigeons.
