I've been doing a bit of digging...
the photo of the "chef" was taken from Divis tower in 1972 (Divis flats still been built in the fore ground) and the soldier was from the Glostershire Regiment. on the regimental museum website there is another photo of the same soldier as part of the CO's rover group, still with the No32 scope fitted. (not a suit sight rubber eye piece)
It looks like the same type of mount as the rifle at the start of this thread,
A pressed steel bracket spot welded midway on the topcover with the scope rings fixed to this bracket, the rings look like a butchered No 32 bracket.
I think 3 years into the "troubles" the soldiers had found the need for optics to aid target identification (prior to the SUIT sight been introduced in 1972 (I think)) and had started to come up with thier own solutions, I have even seen photos of IWS's been used in daylight to identify firing points.
the nature of the conflict changed so quickly in the first few years anything was worth trying, it may have just given the soldier "the edge"
As a young Armourer before a tour of Northern Ireland I was warned by my boss about the "illegal" modifications that used to be done, including the fitting of single point sights and pistol grips fitted to handguards.