There are two sorts of sling swivel available Semper Fi. There is the ORIGINAL, Army issue swivel, called a 'SWIVEL, sling, trigger guard' used on the No4T, the No8 and the L42 and then there is a commerial job that does the same thing ....., but it's noticeably different.

I won't repeat myself here as hopefully someone who is a little more computer literate will bring it up again. If its originality you're after, then ou need the correct Army one.

Try BDLicon first but I'm sure someone on the forum will be able to help