A Brief History of the Marque
Established as a bicycle firm in 1898 at Rue des Verriers, Saint-Etienne, motorcycle manufacture commenced in 1925 using Moser engines. In 1926 J. Monnier became involved in the company,
Several of their larger machines were marketed under the Hellessen brand, mostly 250 and 350cc models using engines from Moser, JAP, Blackburne and Zurcher.
They also established the LSN brand (LouiSoN) and these were sold to Fonlupt, Dobro and possibly other manufacturers. (Note that LSN and Hellessen are homophones)
They built lightweights using Sachs 74cc and 98cc in the 1930s, and cyclomoteurs and mopeds in the early 1950s using VAP 48cc engines and possibly Ducati Cucciolo.
Sources: Wikipedia NL. Didier Mahistre.