Old French bicycles have many compatibility issues. One is the headest and fork. It uses metric threading (25 x 1mm) versus the more common English /ISO stasndard (1" x 24TPI). If the headset was worn out, it may have been difficult for the original owner to find a replacement French threaded headset. Consequently he may have had to buy an English/ISO headset and then a new fork, to fit the headset.

Also, French forks require a 22mm stem while the most everbody else uses 22.2mm. If the owner wanted a different stem , again he may have found it difficult to find a French replacement and resorted to a 22.2mm stem, which would have forced him to replace the forks and headset. Stems can be sanded down, but it's time consuming and this may not have occurred to the owner.

The BB shell is very interesting in that it certainly looks like a reapir/replacement, yet it has what appears to be the holes for the original serial number plate. It's also the original color. I'm wondering if, given assumed situation with fork, the original owner ran into similar issues with the French threading on the bottom bracket and attempted some kind of solution.

All the signs point towards an early 1970s, French manufactured Peugeot, so the fork is definitely an aftermarket replacement. There should be a two character. alpha-numeric code on the fork which will tell us when it was built.