Seeing the SSS plate on the coupe on another thread reminds me of another which was registered SSS715R. It was apparently a 1979 model in red and was for sale in Practical Classics, August 1991. The number still lists as being on a 180B SSS according to Cartell, but because DVLA is on its current nightly shutdown I can't see what its current status is.
Just checked SSS715R on DVLA, no tax on it since 7/10/91. The odd date suggests the tax was cashed-in. Wonder if it's still around?
Recently purchased press photos of the later type 810: