Can't say I know much about the, neither. I believe it was a Pays Basque based producer as I've only ever seen them in Southern France, an I acquired the one i owned there, but may be wrong. They also produced motorcycles, perhaps other stuff too. At some time, probably the 50'ies, they must have merged with Peugeot, as some of their bikes were perfect rip-offs of UO8's except for "Terrot"-decals. Must have ceased production in the early 70'ies. I doubt that they ever produced anything high-end, but my Terrot "UO8" was a very nice bike - and your lugs look like they could be Nervex, so maybe the tubes are Reynolds 531. Interesting bike.

I think the luggage rack is a later addition. Stem looks original. Steel Rims?