KtK has got it in one. One pic does indeed describe a thousand words. The old L2A1 SUIT sight from the L1A1 rifle was an OK sight in itself but the interface mount between both these sights, the A1 and 2 and the rifle was, well, dire if you really want my opinion. Hence the term Shooter Usually In Trouble. The A1's seemed to go by the board quite quickly but a few did hang arounbd for a long time. Someone told me that AVIMO bought them all back when the A2's started coming on stream. The internals were the same just the overhung shade and TRILUX lamp button were different. The A1 type button overhung and got lopped off but you could use a later SR (Saunders Roe Technology) trilux lamp anyway.
So said, these buy-back A1 type SUITS were refurbished by AVIMO in Taunton and these are the ones that were eventually sold off commercially to other Armies, such as Israel who wanted their troops to suffer. You'll note this by the flat fronted OG shade on a lot of the foreign ones
The ribbed eye cups were a bad idea because by putting/pressing your eye up to the rear just caused the ocular lens to mist up so they changed the eye cup to the straight tubular type and as KtK says, this didn't alter the designation at all, it was just a B class modification.
I can confidently say that the SUSAT sight was the only part of the L85/SA80 that wasn't subject to any serious complaints. It was solid, tough, reliable, waterproof (unless you put it in the dishwasher of course.....) well liked, easy to use and squaddie proof. In the later years there was meant to be a vented rubber eye cup to prevent the ocular lens misting up but I never saw one. The sight also cost more than the rifle! I used to keep an unserviceable one (with a broken mounting base and with the grat taken out) in my pouches just to use as a prismatic 4x telescope. Gave it to my son when he was a School Cadet to use and when he left for Uni, he gave it to the Warrant Officer who still uses it
Good illustrative pic KtK. Thanks
PS. The Universal mount on the SUIT was for a picatinny rail ((correct me if I'm wrong KtK) and ordered by the Kuwaiti Army originally.