Yeah the sterling smg bayonet could be a spike during ww2 its basically the same one once fitted to the Sten but they also made this number 5 with the same mortice fitting and sterling made their own post war, pretty much the same as this but with 2 screws or rivets in black Bakelite grips that didn't wrap all the way round Muzzle rings differ between them as the smg's were a 9mm round and a smaller barrel dia than the full fat 303 leeI vaguely remember the SMG bayonet having 2 screws, like the SLR one. The same bayonet if I remember rightly, or at least they were interchangeable. I think the WW2 era ones were spikes..?
The idea of an SMG fitted with a bayonet always made me laugh. If they're that close you might as well kick them in the gonads...!
its a minefield unless you can find good references mate, throw pistol bayonets (i kid you not) into the ring along with pig stickers but with a similar blade to this and later stuff instead of a spike and its a real nightmare of a rabbit hole to be falling down
Then you had the number 8 for the SLEM that didn't get adopted, that used number 5 blades and when you get to the SLR proper (L1A1) there are about 4 different versions from different factories, same blade shape as this one but varying lengths L1A3 and L1A4 is where the settled around 74 i think, these are what you would remember from your service I guess mate?