GM participated at Le Mans in 1925 with a 1500 cc 10 HP, which had front and rear wings, running boards and a very bulky rear end. It could be the same car with reduced bodywork.
PS. Although the radiator is kind of characteristic and I had a closer look on the GM for a former puzzle by Joao, it would have been harder if there hadn't been the "GM" written on the hood.