Congratulations ...
I remember this one from the CGN discussion about it ...
The SMLE No 1 Mk V & Mk V1 along with the No.4 Mk1 "Trials Rifle" all used a stamped sheet metal cut-off, as opposed to the forged ones on the earlier rifles. You can tell the difference by looking at the round part that forms the grip. The early style is solid with a hole drilled in it, while the sheet metal unit has a gap where it was rolled over to form the round part.
Regards,
Badger