You have a very nice BSA sporter as you said, BSA made most of what we call "Lee Speeds" but are all BSA sporters really, just some had "Lee Speed" on the Butt Socket & that type of rifle got the name "Lee Speed"

Yours is the later type how late I could not tell you, has no mag cut off, some didn't, one way maybe to see if the trigger is the SMLE type or MLE type & is there a small groove on top at the back of the bolt were a dust cover would click into ?

The safety is just the half cock, just one pull of the cocking piece .

Lovely piece wish I had her here, has all the bits I like & not the bits I dont like !