My 88/89 Corsa Extra SLX is 27.0.. I would say that with the external cable routing and also the fork crowns you have that your frame is either as old, or older than mine - and almost definitely not SLX.
I suspect that the extra boss/pump holder/ number holder is an addition - I believe you could order them with additional, custom bits, either that or it may have been brazed on after.
My 88/89 Corsa Extra SLX is 27.0.. I would say that with the external cable routing and also the fork crowns you have that your frame is either as old, or older than mine - and almost definitely not SLX.
It could be a Corsa, made from SL? See here: http://www.bulgier.net/pics/bike/Catalogs/Eddy_Merckx-90/p6_Corsa.html
Or, have a look at the other merckx catalogs here: http://www.bulgier.net/pics/bike/Catalogs/
I suspect that the extra boss/pump holder/ number holder is an addition - I believe you could order them with additional, custom bits, either that or it may have been brazed on after.
Just an opinion, not fact!