When the British began developing a shortened version of the No4 Lee Enfield in 1943 (which would become the No5 MkI "Jungle Carbine"), the development process included work with some rather older rifles. What we have here is a 1922 production No1 MkV rifle cut down as a trials prototype for the carbine development program. The No1 MkV was a trials gun itself from the early 1920s which basically gave a rear aperture sight to the classic MkIII SMLE. Unfortunately, I don't have any specific details on the testing or use of this particular example, but I think it is a fascinating example!