Check the serial number against published references or call the company that made it.
Find books on the maker.
By the serial #
Find a book with sn's from that maker.
You will have to call Rossi to find out.
Blue Book of Gun Values
You will have to call Browning to find out.
Gun shops, gun stores, pawn shops, library, on line auctions.
You can often find a Winchester Centennial 66 at a gun show or in the hands of collectors. Due to their age, they are not likely to be found at gun shops.
Find a book of sn's that has been published on the weapon.
The Blue Book of Gun Values has sn data you can use.
The gun was made in 1919, nice find!
Age is 1966 from the AB prefix. You can find diagrams at Gun Parts Corp. web site.