I think you are right, this is a commercial knife.
I have a book by Jean Fontvielle called "Couteaux de combat". It is written in French, so my translation may not be totally correct.
The civilian knife is marked "Le commando Super Nogent" - these were used by French troops in Algeria and Indo China in the 1950s.
There is a military version - these are marked F.O.M. and a number. - the highest number noted is 2000.
F.O.M - Forces d'Outre-Mer - (Overseas Forces)
These knives were issued to the Fusiliers de Marine Commandos in the Algerian war (1957 - 1962).
The same design was also made with a bayonet fitting for use on the US M1 carbiine which was used by the French - these are very rare (about 700 made).
Hope that helps a little.
Some more details from "Les Couteaux de Nos Soldats" by Lecoeur and Rouquier. Knife designed by Louis Henrion around 1953. He was a veteran of the 11th Shock batallion, a Free French Army unit modeled on the US Rangers. About 200,000 examples made for commercial sale. Blades made originally by Ets. Conversat then from 1964 to 1974 by Societe Dussaussay-Galtier in Nogent. That's the cutlery capital of France. There are many photos showing French troops and marines wearing this knife or the F.O.M. version which had an all metal scabbard. The bayonet variation came with this metal scabbard and was part of a patented "system" which included two versions of a bolt-on retainer that attached to the M1 carbine barrel to lock the pommel of the bayonet. The bayonet is known as the "FUMACO" knife-bayonet. That stands for Fusiliers Marins Commandos. They are famous for action at Dieppe and Ouistreham on D day.