My observation of a National (or NATO) stock number on the scope and the container would tell me that it's post 1975, when the NSN came in to use. 1240-99-963-2063, FSC "1240" is the Federal Supply Class for 'optical sights and range equipment', the "99" is the country code for the UKicon. The stock is notably shortened or what I'd call a sporter, but let me preface my observations with the fact that I know next to nothing about the Enfield.

The NSN on the box with the FSC of 1005 encompasses guns, "thru 30mm"