Savage 99RS - introduced in 1932. Originally had a Lyman 30 1/2 peep sight, that changed in late 30's to the Redfield 70LH. It was the premier hunting model, though the engraved 99K existed for most of the same time and would have been the top of the shelf 99. The sling studs are distinctive to the prewar 99RS, very rarely do you see them on any other 99. The double "rings" at the front of the forearm are also unique to the prewar 99R / 99RS.

The "prewar 99RS" like yours was last catalogued in 1946/1947, but VERY few show up after 1941. Just a couple have been seen, iirc. Another style of 99RS was introduced around 1950, but the stock configuration was totally different.

THAT is a beautiful gun, and extremely collectible. Take good care of it, and thank your step-dad profusely.

“The Savage 99 Pocket Reference”.
All models and variations of 1895’s, 1899’s and 99’s covered.
Also dates, checkering, engraving.. Find at www.savagelevers.com