Manufactured by Comet Motors, Bruxelles, 1949-1951. These were powered bicycles and tandems with a 63cc two-stroke auxiliary engine mounted in the hub of the rear wheel. The engines were from Société des Ateliers Hanrez, also of Brussells, and were badged "Comet Hanrez", so it's possible the companies were the same. These engines were fitted to mopeds built by Chemineau of Saint-Etienne in 1954.
Sources: A-Z der Belgische Motoren, OTTW.