Thanks Guys. rgg_7, the engraving says "Rigby 350 Magnum" matching what Hivus said. It came with a box of ammo as well which was nice.

Honestly, I'm too green on my Mauser lore to answer any of the questions about stepped receivers or slant box magazines. I've seen a few references here or there on this site, but that's about it. This is by far the oldest rifle that I own and I'm still wrapping my head around all of its intricacies and trying to figure out some of the do's and dont's for vintage rifles (IE, whether to do more than just clean the stock, or try to track down an OE butt plate for it).

I was a little thrown by the cocking piece sight. Definitely not an item that I've ever seen before. Was it designed to use in addition to the sight leaves, or in place of them? Also, judging by the two unoccupied grooves on the rear side of it, I'm kind of wondering if it isn't incomplete. Is there a good detailed photo of one somewhere that I could compare to?

Thanks again.