You have received lots of good advice already. The butt-plate looks original LB that got paint with Suncorite black paint in England postwar. Interested to see better pic of the leftside receiver showing all the script and varoius numbers. Notice they restamped the LB serial number to the left of the factory script. There were a number of arsenals that did work in varying degrees. Fazakerly seemed to be the most prolific. A clean set of "furniture", that's a stock set in Enfield language, is often more costly than the sporter.
Cheers