These quite roughly cast and not too well finisehed stems were all the rage in the UK in the 50s long before the likes of TTT and Ambrosio started to appear on the scene, and they made such a change from the ubiquitous GB "Spearpoint" and girder stems. I eeven recall, in the late 50s changing over from one of those hand-made fancy-lugged steel jobs onto a Pivo. The real "must have" feature of these French stems is the "Y" shaped flute running along the top of the stem and down the front clamp because you could pick this out, along with the crescents cast in at the rear of the stem, in a colour either to match or contrast with the colour of your frame. Having said that , most of the PIVOs I have seen have the paintwork in red Why? you might ask. Well. in 1957 a guy called Kack Anquetil won the Tour de France using a Pivo, with red-painted crescents. He returned in 1961 after a few losing years, to win again but this time using the latest model Pivo stem complete with red-painted "Y". And again in '62 '63,'64 etc etc Five Tours and other major wins all on crappy PIVO stems. He was still using them in 1966 on his all_Campag equipped Gitane.
I don't know who made them, possibly a forerunner of ATAX, but the stems appeared as PIVO, Milremo made for Kitching and Bertin ) and possibly in their best incarnation as Phillippe - all the same though..They were standard equipment on Helyett, CNC Speciale, and many other top French bikes of the time.
Norris Lockley