I haven't taken pictures of it yet, but it's a 1957 BSA Imperial Featherweight in .30-06. It has a built-in muzzle brake, factory sling swivels, and a gorgeous Schnabel stock.
The action is a Mauser variant, with a Winchester 54-style rib along the bolt as a stabilizing guide. The ejector also comes up from underneath like a 54; the left lug is solid. The cocking piece is tall and skinny like an SMLE, and sticks out the back when cocked as an indicator. The safety is on the bolt shroud, a lever hinged forward and back. The floorplate has a commercial Mauser style release lever in the trigger guard.
BSA made that style of rifle from the mid '50s to early '60s, then went to a new design with a small extractor and plunger ejector, similar to the post'64 Winchesters. I like my older model much better.
The rear sight is well ahead of the receiver, dovetailed into a knot in the barrel, like some of the modern high-end rifles do. Except this one was made in 1957.
The muzzle brake is just slots at the end of the barrel. BSA didn't keep that feature long, and reportedly had a "range hood" that could be attached to block the ports when other shooters threatened you with torches and pitchforks.
The top of the receiver is dovetailed to take Parker-Hale type scope rings. Which are, of course, oddball British bits... it looks like I'll have to find some rings first, then buy a scope to match.