While Bruce Gordon didn't fillet-braze or otherwise do his 753 test, there was a fillet-brazed 753 bike in the last René Herse catalogue from the 1980s. According to Jean Desbois, who was the builder then, Reynolds in France supplied the brazing rod with the tubes. So I assume they used that for the fillet-brazed bike as well. Apart from the catalogue bike, I never have seen a fillet-brazed 753 Herse, though... so maybe it was a 531 bike that they put in the catalogue, and then decided it would sound better if they said it was 753. (The did fillet-brazed 531 bikes for riders who wanted superlight, and they also did 753 bikes.)
I have never heard mention of the 753 test in France - Reynolds had their own distributor in France, and he did a lot of things his way. For example, the thinnest-gauge 0.3 mm 531 supposedly was a product available only through the French distributor, who held the rights, rather than direct from Reynolds in Britain. -- Jan Heine Editor/Publisher Vintage Bicycle Quarterly c/o Il Vecchio Bicycles 140 Lakeside Ave, Ste. C Seattle WA 98122 http://www.vintagebicyclepress.com