Peter your right the TR does look a little high up on the butt socket and strange the number is missing. It does not have a SKN serial number.
I actually got this from ROF Nottingham when BAe closed it down. It did have a tag attached
with more information. I remember putting the tag safely away but can't find it at the moment. If I recall correctly the rifle was described as a TP rifle and then amended as TR.
If I do find the tag I will post a picture.