Well, I'm the current custodian of the Lee Speed - thanks, Derek!

Very interesting rifle. A few things stand out to me ...

1. The handgrip radius seems much tighter than other Lee Speeds shown on this site. I have to wonder whether it isn't a replacement as well?
2. There aren't any markings on the rear of the receiver. The other BSA I've found has BSA stamped in the "normal" location. There is a "nitro-proved" stamp on the top of the barrel however.
3. As Derek mentioned, the fore-stock is a replacement from an SMLE.

Haven't shot it yet, but a .312 bullet will enter the muzzle pretty much all the way - could that be Metford rifling? If so, what might be the approach to getting it to shoot?