Source picture: Patented Systems
[Classication = Group 3(1)]

bignansportdesmo1923 bignansportdesmo1923left

bignan5 bignan1
Source: Bignan Entry: The Complete Encyclopedia of Motorcars : 1885 to the Present / edited by G.N. Georgano; London, Ebury Press, second edition 1973.

‘Mystery’ (fake information) solved (2022). Némorin Causan was supposed to be the inventor / creator of the Bignan Desmo. Bignan descendant Michel Bignan explaines in this article that this was not true:

Article Michel Bignan

Pictures of the Bignan Desmo. These cars were known for their square radiator with a winged stork on top, which could be vaguely seen in the picture. This is a 1923 Bignan 11Cv DESMO Sports. The engine is a 2L single OHC with Desmodromique valves. The picture was taken in 1925 during the ‘Côte des 17 tournants’ (a hill climb near Dampierre in the Chevreuse Valley).
(photos collection Karl Ludvigsen Library and collection Pascal Rousselle) Source:
This link is broken since September 2021. The website: is still working.

The Bignan is classified as a Group 3 (1) system, which means a “positive” cam with a “negative” camfollower
The perspex model is classified as a Group 3 (2) system, which means a “negative” cam (groove) and positive camfollower

pictures of the perspex-model = Group 3(2)