My buddy sez to tell you it's a b*tched pellet gun and offer you 5 bucks for it.
It is a Short Magazine Lee-Enfield rifle Mark III* and it was built by Standard Small Arms in 1918.
It had a COMPLETE rebuild in 1944 (Factory Thorough Repair), so it served through BOTH World Wars. AFTER World War Two, it was sold off, made into a budget sporter.... and now you have it.
Being that I'm not yet COMPLETELY corrupted by the prospect of owning EVERY Lee-Enfield ever made, I suppose I should tell you that this is the only 1918 SSA I have come across. I think it must be very early in the 1918 production year, before they had the new stamps made for NRF (National Rifle Factory). SSA was a private company that built rifles for the Army only during the Great War. They were nationalized very late in 1917 under the name National Rifle Factory Number 1 (metal work) and Number 2 (woodwork). Plants were closed at the end of the War, of course.
BIG problems at SSA/NRF: Govt wanted rifles and wanted them NOW but would not give SSA the priorities they needed to equip the plant but the Govt wanted rifles RIGHT NOW. How they were supposed to make the things with no machine-tools no-one could say but the Government is omnipotent, omniscient and omnipresent, sort of like God but, unlike God the Government never forgives. So they were shafted from Day One but they did the best they could, setting up for one part after another, shipping parts to Enfield for finishing for about 2 years before they turned out their first whole rifle. Once the Government in its divine wisdom took over, there were no problems getting tools, but they already had what they needed, so the original people took a licking and the Government took the credit.
In World War One, Standard Small Arms built only THREE percent of the Lee-Enfields actually produced in Great Britain. This figure shrinks further when you consider the number of rifles built also in Australia and India. They are rare, no guff.
And YOU have an SSA. I can think of a lot of serious collectors who want one. Took me 20-odd years on a minimal budget to run into one and it's no better than yours.
Give yourself a pat on the back. I think this would make rather an impressive centrepiece to a World War One Lee-Enfield collection (7 Mark III*, 6 Mark III).
PS: Friend, you REALLY want to see 'slick', put a couple of drops of oil on that bolt.... then work it fast.