Anderman
Donor
Now the HS 404 not only was it a development of the earlier Oerlikon guns but it and its design was well known to the British and ultimately its technical drawings are far more likely to be available earlier than the German and Russian Weapons ever would be.
Unlike earlier Hispano-Suiza gun the HS.404 is not based on the Oerlikons guns
https://en.wikipedia.org/wiki/Hispano-Suiza_HS.404#From_Oerlikon_to_Hispano
The HS.404 is gas operated. The Oerlikons are API blow back operated
https://en.wikipedia.org/wiki/Oerlikon_20_mm_cannon