If made from a parts kit, it would have the makers name stampted on it, and originally been on a form 1
Not all of them were marked with the "CBS MK8" Marking, (Mine isnt) that had to do with what market it was intended for when marked. the ones with the CBS markings were intended to make the U.S. oversee'ers happy.
, as was the read manual before use that is stampted on that one, below the Dagenham address on the left side of the trigger (mine dont have that either, it has the emporter Lanchester USA Dallas Tx below the Dagenham address, then all of it covered at the factory with the crinkle paint)
All of the serial numbers should start with "SA" though
Spare parts are not that much of a problem, as most running parts are the same as a MK6, the barrel is a MK4 smg barrel with a slight notch for the "popsickle stick" to run under.....most everything wiselite sells as spares would work..including spare firing pins
Here is mine, note the 'SMG" and L2A3...