The auto-5 was produced by F.N.(Fabrique National) of Belgum starting in 1952 until the 70's I believe.(Production after that was in Japan). My Auto-5 was produced in 1965. It had a butt plate on it marked Browning Automatic on it with the F.N. marking in the middle.As for the barrels, they should be stamped *special steel-12 guage-shells 2 3/4 or 3" (on my barrels this is stamped on the right side) On the left side it should be stamped Made in Belgum. The simplest way to date your gun is through the serial #. If you can get the serial#(located on the bottom of the reciever at the front of the loading port) you can find the year of production here:
http://www.midwestgunworks.com/page/mgw ... -5-history
I can't say how much this gun is worth in U.S. funds, but in Canada they go for between 350-500 bucks. I love My Auto-5. It is extremely reliable(you must keep the action clean) and so easy to handle.
If you need any more help, let me know.