They did infact sell an SLX framed model in Europe in 1991/1992, it was also offered as a frame only here in the UK as part of the 1991/1992 model year...same colours as the 753 chorus.
This is most definitely SLX due to the helicoil ribbing evident when I rammed my finger up the chainstays and seattube...oooo eerrr matron!
Frame No is - 0042590
Rear O.L.D 130mm on this too.
A nice compliment to my Record equipped 992 in sig
Out of interest, what seatpost size is this? and also whats the rear O.L.D of yours- I was expecting it to be 126mm for the most part of a 7 speed Chorus groupset I've got for it, however its actually a solid 130mm so looks like I may have to rethink the groupset aspect, maybe 8 speed newer chorus so I can at least use the wheels out of my 992...I must also add better pics!
Cheers for post size. Well my Record 8 speed cassette hub wheel @ 130mm fits perfectly but my Chorus threaded freewheel wheel @126mm is like 'sausage up an alley' in there....so I am where I am - At least I can use one set of wheels for both bikes.