Glad to see your post. Good timing .I purchased a carbine lee speed by Rigby yesterday. Looks to be the same as yours.Marked lee speed with barrel engraved Rigby st Jamess st london. Cant wait to recieve it. Turned the net upside down to find info on this rifle appreciated your post.
Like you I was unsure of rifle being original or built after by Rigby. Decided to go ahead with purchase as the one Ive found appears to be in very good condition. Bore is a unknown though it has been shot with .311 projectiles and didnt group well.
The bore visualy looks very good with no pitting and sharp rifling.
Taking a chance but Lee's dont come up or stay on the market very long over here.
Id appreciate any more info that you find on the Rigby Lee speed.
Congratulations on your find. Heres the sellers pics of the one Ive got on the way.
The obsession with Lee speeds started with a look at a Army navy lee from a forum member here.
Cheers Mick