Beretta's first auto-loader was the gas-operated Model 60, introduced in 1956. It was followed by the Model 61 (an improved version of the Model 60) in 1961. By 1965, the Model 61 was replaced by the Model 300 Series of auto-loaders, which survived until the A-301 was introduced in 1971. By 1980, the A 302 was introduced and by 1985, the A 303. 1988 saw the introduction of the short recoil operated (blow-back) model 1200F. The A-304 was introduced in 1992 and the A-390 in 1994, soon evolving into the AL390, followed by the now more familiar AL391 in 1999.
Hard to say what "buddies" gun may be, but if from the '70's. likely an A-301.
As such, and depending on condition ( I'd want to shoot it first to check on "function" too, both with heavy & light loads ) $ 300 - $ 400 if it has a rib, and up to $ 100 less if not.
The 301's came in a standard field version, both with & without a ventilated rib in 12 and 20 ga. Chromium molybdenum steel barrels & fixed choke. 24-1/2, 26, 28 & 30" barrels
( actually 62, 67, 71 or 76cm) There were also a Deluxe, Super Deluxe and 12 ga. 3" Magnum version.