List Members:
Thanks to all who replied.
Many suggested PX-10 seat post should be 26.4, not 26.2mm. Existing post is English-made; no diameter inscribed. Original saddle was Ideale 2001 leather-over-nylon on a Simplex post, but I wanted solid leather (Brooks). Dealer offered an Ideale 90 IR, w/straight post. Dealer had to sand post, and just this year I sanded even more 'til it finally fit right, so while I don't think anyone squeezed the lug, that is still a possibility. Perhaps someone could tell from the photo whether the lug looks squeezed. Here's a picture of the existing setup:
http://www.flickr.com/
I have an SR Laprade post inscribed 26.4, and it doesn't want to go in. Another bit of trivia is that on page 227 of The Custom Bicycle by Kolin and de la Rosa (1979) the author states, with some reservation, that a French bike with double-butted tubing is likely to have a 26.2 or 26.8 mm post, and without db tubing 26.2 or 26.4. I think I'll let my LBS check it before ordering a new post.
I often see comments on eBay about the presence or absence of insertion marks on vintage seat posts, and know myself how hard it is to avoid scratching up an alloy post. Would it be better, or even possible, to use an undersized post in combination with an aluminum or nylon insert? BTW: One person asked about the year model of my bike; I wish I knew for sure. Purchase date was Jan 1981, but Bicycling Magazine reviewed a PX10LE just like mine in Dec 1977.
John Hurley
Austin, Texas USA