Looks like your seat clamp binder bolt has been cobbled together. A BF member has (had?) NOS ones for sale on ebay. The proper one is scalloped, so you can't just put a standard binder in there.
Probably a 27.0 seat post
My Frejus from '72 has the same binder. (Edited out for better info later)
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72 Frejus (for sale), Holdsworth Record (for sale), special CNC & Gitane Interclub / 74 Italvega NR (for sale) / c80 French / 82 Raleigh Intl MkII f&f (for sale)/ 83 Trek 620 (for sale)/ 84 Bruce Gordon Chinook (for sale)/ 85 Ron Cooper / 87 Centurion IM MV (for sale) / 03 Casati Dardo / 08 BF IRO / 09 Dogma FPX / 09 Giant TCX0 / 10 Vassago Fisticuff
Last edited by Ex Pres; 07-31-09 at 07:33 AM.