Hello. Fazakerley isn't better than BSA, or the other way round. It's just a different manufacturing plant, located in Liverpool in the UKicon. There were five different manufacturers of the No4 Lee Enfield during WW2; three in the UK, one in Canadaicon, & one in the US. The US company contracted to produce them was the Savage Arms Co of Chicopee Falls, Mass., & the Canadian rifles were produced at a new government set up facility at Long Branch, a suburb of Toronto. In the UK Fazakerley & Maltby were both government ordnance factories, whilst BSA was a commerical manufacturer brought in, & was already producing the SMLE. Going back to the rear sight, the example fitted is quite acceptable on any No4, though in this case probably got fitted post war, as by then many of the simplified cruder wartime rear sights that had been approved to speed up production, were being replaced for the Mk1 rear sight as fitted to your rifle. Fazakerley was the biggest source of supply for such replacement parts.

If you ever do change your mind, as mentioned, your rifle would make a nice restoration project back to original military trim as the metalwork appears to be intact.

Nice rifle, enjoy regardless!