Looks like your quoted post disappeared, but I saw it in my mailbox. I don't mean X4. SL, X3 and X4 are different models from different years. You can spot an X4 from miles as the head tube logo is pantographed (engraved), no decal.



Both X3 and X4 had collarless fork crown, but here you can compare them - check the 83's cdm to see those had the blue winged logo, not the gold, and flat fork crown, then the '85 Specialissima, then the 86' X4, they have nice detailed photos.
Another hint is this bike is the 85' Specialissima, is the lowe head tibe lug B. on the X3 and X4 it is cut into the lug, on yours it is embossed.
www.speedbicycles.ch/museum/index.html