The 1950's 99R/99RS is totally different forearm. The forearm is wider, with slant outs in front of the receiver. Most don't have a jewelled bolt, that came late in the 50's. A different checkering pattern, yes, and different studs for the RS. All 99R/99RS's in the 50's came with sling eyes intended for use with swivel hooks to attach the sling, and they all came drilled and tapped from the factory with standard screws for mounting scope bases and with the "SAVAGE MODEL 99" stamp on top of the receiver stamped to the side to make room for the scope base screws.

1953 99RS forearm:

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“The Savage 99 Pocket Reference”.
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