Manufactured by Louison at Rue des Verriers, Saint-Etienne, established 1923.
Louison also used the L.S.N. marque, the letters from the name LouiSoN. Hellessen is the sound of LSN when spoken aloud.
The Louison company was acquired by J. Monnier & Cie in 1924.
Motorcycles were built under the Hellessen brand from 1924 ~ 1933.
A 1924 advertisment shows J. Monnier as the firm producing Hellessen. Offered are machines with OHV 250cc Moser and 350cc Zurcher engines, with optionally JAP and Blackburne.
A 1928 model with a 350ccc Moser engine has much in common with the 1928 350cc Styl'son RF.
Advertised in 1928 with 250cc and 350cc engines. Advertised in 1931 was a BMA Louison which had a 98cc Sachs engine.
The Hellessen was also sold by J. Monnier & Cie under the Monnier marque.
Sources: Motos dans la Loire, stylson.net, lva-moto.fr, OTTW, Didier Mahistre