Marius Mazoyer, previously involved in aviation and bicycles (and famed for his flying bicycles), established the firm Mazoyer at 13-17 Rue Thiollière, Saint-Étienne in 1901. In 1928 they built motorcycles using JAP, Moser and Zurcher engines, with the first machine believed to have an engine of their own construction.
The name Metalloplan came about as a result of Mazoyer's desire to construct aircraft from metal, as he was in the habit of rolling the wooden ones up into a ball. He destroyed some ten of them, it is said.
There does not appear to be any relationship with the machines built by René Mazoyer in the 1950s.
Motos dans la Loire states that post-war, from 1951 to possibly 1958, the company produced cyclemoteurs using engines from Le Poulain, Mistral and Junior. There are very few references to post-war models.
A bicycle company named Mazoyer-Besset (Paul Besset) was founded in 1928 in St Etienne, and built Coq de France cycles, and later bought the Racer marque.