Géco-Herstal is a way for Gillet (van Herstal) to avoid import duties in France. The parts came from Gillet in Belgium and these were combined with French parts to create models that were very different from the Belgian Gillet models.
This is a 250cc OHV from 1930. Engine is a Zurcher that was known for its solidity and sporty character.
Motorcycle is not completely complete but still a very nice basis for restoration.