Bob,
>From the frame number this is an (early?) 1982 frame. I was under the impression that SLX began in 1983 when the drilled lugs were discontinued. SLX Frames had 27.2 seat posts. I know the earlier Cinelli's had 26.2's. Maybe the seat post is hogged out, or maybe the seller has tried (incorrectly) to measure the diameter without actually fitting a seat post? These later Cinelli frame numbers began with the year of manufacture. What year is yours?
Jeff Pyzyk
Milwaukee, WI