This a lovely bicycle and a fantastic bargain. There are some clues that allow us to date it to a narrow range. The Simplex rear dropouts are the 2nd version of the type 3480/81 dropouts. The original version, which had the Simplex name embossed into the rear web, was introduced in late 1972. The 2nd version, as seen on the OP's bicycle, with the Simplex name on the leading web, is first seen in the 1974 catalogue. The style of Reynolds decal used on this bicycle was replaced in 1974 with a version having a wide gold band a the bottom containing the company name and location. Bicycle manufacturers often had excess stock to use up and poor stock rotation could delay this, but typically the older style tubing decal persisted no more than a year or two. The combination of Simplex dropout and Reynolds decal suggests 1973-1975 manufacture, which is consistent with other frame features.
Outside of the OP's stated replacements, the components are consistent with this time frame and are likely OEM. Weinmann brakes on a French bicycle of this era are atypical but not unknown. The Durifort fork decal is in opposition to the full 531 decal and appears to be an addition by the previous owner. This raises the question of the whether the decal was transferred from the front fork. Besides the contrasting colour, the tips of the blades appear to be domed, unlike the fish mouth ends used on the stays. Given the era and level, this suggests a replacement. I also suspect that the fork will not have the reinforcing tangs as seen on the stay bridges. Given the suspect fork, I would closely examine the top and down tubes, in the area immediately behind the lugs, for signs of a bent frame (i.e. ripples and other tube distortion, cracked paint, touch-ups,etc).
The frame itself exhibits very nice workmanship for the era. It appears to be high grade, as opposed to a production frame with Reynolds 531 DB. The frame is almost certainly 531 DB but it wouldn't hurt to verify it by measuring the seat post diameter, which should be 26.4-26.6 mm,assuming has been correctly sized and a metric seat tube (i.e. 28.0mm outer diameter).
What I don't know is whether these were manufactured by Velosolex or contract built . Hopefully, other members can provide further enlightenment. Thxs for sharing the pictures. Enjoy your new acquisition. Pic assist....
