That's cool, but all of them could have any safety, none (half cock only), bolt (thumb) or shot gun type (also thumb) not even the charger bridge is a indicator of age, as they were fitted to some of the MLE actions, the trigger pull might as the early MLM/MLE had a single stage pull SMLE's had two stage, maybe just screw the front wood off, if that's not too much trouble ?

Im thinking it will be Ok to tighten as is most likely the early action but hate to split the wood .

Just thought id add some pic's of both types of Butt bolt & fore end .

SMLE

Bolt of SMLE

MLM-MLE most BSA Sporters/Lee Speeds

Bolt