I would recommend Herbert Houze's book "Winchester Bolt Action Military and Sporting Rifles 1877-1937." He covers the Model 51.
If you have one, consider yourself extremely blessed, and don't let anything happen to it! Only 75 were produced, all handmade as presentation rifles for Winchester's board and various VIP's.
Go to Proofhouse.com and search the Winchester sn tables
Browning never made a Model 51 shotgun.
The Wikipedia article on "Area 51" seems to have a good overview. It also has links to additional sites.
If the Model 51 is in very good condition it should bring $250 - $300.
You can try Numrich gun parts, ( e-gunparts.com )
It's an inspection mark. If your interested in more information about the Model 51 there is a survey currently being conducted for them on the Remington Society of America under current research.
x = -51 -x = 51
The Model 37 is a pump gun, and the 51 is a semi-automatic. I doubt seriously that the barrels are interchangeable, since they are totally different models.
7.65 mm is usually .32 Automatic Pistol. The .308 is 7.62 x 51
What Model 51 pistol or a rifle and what model?
Savage. Model 51 & 951.
89 percent of 51 = 45.3989% of 51= 89% * 51= 0.89 * 51= 45.39