Roger,  It’s very similar to some of those shown in Campbell’s SS book, but not exactly the same.  Best photo of that style is shown on p. 148 of Vol 1.  The adjusting nut at the top of the shaft is shaped differently, longer on yours.  But maybe this is another variation he wasn’t able to photograph.  Possibly one of the repros made by MVA or the Ballard Co., but no doubt Bert can tell you for sure. 

Sought after items, whether factory or not.  The Canjar rests for Model 52s sell for $200+; I know because I bid on two & (as usual) lost.

Bert H. said   That stated, they look very much like the Stevens rifle palm rests.

Bert

  

The illustrations (woodcuts) in late Stevens catalogs don’t provide enough detail to identify these positively as Stevens.  However, if they are Stevens’ designs, they must be Paul Shuttleworth repros, because it’s not credible that two original Stevens rests would have survived in “near mint” cond.–they weren’t offered by Stevens after 1918.

One way to find out for sure would be to send photos to CPA.  Paul died last yr in his ’90s, but the company (under his daughter) is still going strong.