Motorcycle presented at the Paris Salon of 1902 (possibly an Auto-Fauteuil) (Bourdache pp 273, 294)
1905 - marketed in London by Gauthier & Co of Holborn. These were engine kits with French components so it seems likely that the firm was the British representative of the French company.
There is a possibility that the marque existed before the turn of the century.
Georgano & Heymann give the following:
Gauthier (F) 1904-1937
The French engineer produced his first vehicle in 1902, and between then and until his death in 1939 he built some 350 vehicles. These were mostly small cars, such as l'Auto-Plume Capri, and l'Auto-Fauteuil, presented in 1927.
Gauthier produced a number of single-cylinder engines, air or water cooled, of 350, 400, 500 and 550cc.
His Léger chassis had a transversely mounted engine, with the passenger seat either above the rear rear wheel or between the front wheels. Engines were fitted according to customer preference. This durable and relatively inexpensive machine was intended for missionaries and pastors.
In 1918 Gauthier presented a cycle car named Avionnet with a V-twin engine, built for military service. It was equipped with a patented suspension. A 3-wheel version was available until 1927.