You would probably get all the information you need ... in detail ... over at
www.RimfireCentral.com on the Mossberg Forum. Some fellows over there know old Mossberg's like the back of their hand.
This should give a start, however:
Model 351K Auto-loading Sporter. NiB: $184 Ex: $153 Gd: $112
Caliber .22 LR. Fifteen-round tubular magazine in buttstock. 24-inch bbl. Weight: 6 libs. Sights: Open rear; bead front. Monte Carlo stock w/pistol-grip. Made from 1960-71.
Information from Gun Traders Guide 30th. edition.