Just acquired a Peugeot frame and fork with the internally rifled Reynolds 708 tubeset - hope to make it into something rideable soon.
Apparently it was a concept tube set with 531 main tubes and 753 rear stays/fork in road tube sizes. The 3 main tubes were not butted, but had 8 flats running the full length (except seat tube where it was only partial).
An example (not mine) built up and a page from the 1994 catalogue (the closest I can find to the model/tubeset) thus far.
Any other information please tag on here!
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CURRENTLY FOR SALE:
Holdsworth 531 Special Team - Cannondale ST400 - SUNN BMIX - Carbon Flite - Specialized M2