Browning never made a Model 51 shotgun.
No
If your over under shotgun was made prior to 1964,then the model of your Browning shotgun should be named the superposed.
If you have a 12 gauge model auto-5 Browning shotgun?Then it was produced by FN of Belguim for Browning in 1923.If you have the same shotgun in 16 gauge,then it was produced in 1928.
Can't answer about "Volunteer" question. Please tell which model. Volunteer is not a model by Browning
Auto 5
What is the value of a 12 gauge Browning shotgun serial J68824?
A bolt action shotgun in 12 gauge.
50-650 usd
Browning did not make a Model 755. Savage made a 755 that was similar to the Auto 5.
Shotgun made by Browning.
If your Browning auto-5 shotgun is a 12 gauge model then it was made by FN of Belguim for Browning in 1907.If you have a 16 gauge model,it was made in 1921.