Not wishing to contradict anybody, your friends BSA looks like a Light Pattern, an early model with a two hole trigger block, push button underlever catch, made in 1919, it also has a factory made foresight protector which is nice and very rare.

The follow on model is the "A" Series, which has BSA Standard etched on top of the cylinder and is very similar but has a sheet metal trigger guard and a trigger adjustment screw, one with the serial no 2344 would have been made in 1937.

HTH

Ben