Dear Mr. Ciardiello
You are right, the letters „OC“ stands for Ondes Courtes.
In the mid 20ies the invention of the Modulateur Bigrille by Ducretet had its limitations regarding the reception of waves shorter than 200 meters. The oscillations were not strong enough to obtain reasonable results.
The solution was simple, just add an additional triode for the oscillator part and connect it to grid1. This triode has a much better Transconductance and both systems are placed in one bulb!
The tube was produced by La Radiotechnique, Suresnes, France
Credit to Willem Breij. Informations retrieved in an older „Radio Historisch Tijdschrift“ The Netherlands.
Many thanks for the precious and very comprehensive information. So far I had found nothing on this tube, not even the code.