Bicycle engines manufactured 1950-1952, Ets Darris, 8 Rue de Richelieu, Paris 1°. 49cc Types H51, H52.
They can be mounted below the saddle to drive the rear wheel by roller, or can be fitted to the fork yoke to drive the front wheel. The marque appeared at the 1950 Paris Salon.
One of these models was fitted to a Hurtu frame and was powered by a Motox engine, for which Darris was the French distributor. The same engine was fitted to the Hurtu CVM of 1952.
That year, 1952, the Darris address was the same as that of Hurtu, so it appears there was a merger.
Sources: calamine.fr, et al.