Source https://www.tapatalk.com/groups/curioandrelicfirearmsforum/gf-marked-wire-wrap-enfield-t3309.html
More reference info on these neat old rifles... please see:
https://www.rifleman.org.uk/Enfield_Rifle_Grenades_and_Dischargers.html
GF = grenade firing
Another: Indian made GRI SMLE grenade firing rifle:
https://www.gunboards.com/threads/1942-gri-grenade-wrap.1245053/#post-11293871