This months tube is an old European output pentode. Meet the EL3N.
This tube was introduced by Philips in 1938 and meant to be used as Class A or Class AB output tube.
Philips data sheet does not give a lot of information besides Class A and Class AB operating characteristics with a measly 8W stated as output power from the latter. I never used this tube myself and the few samples I can show were leant to me. Since the data sheet does not give any plate curves, I took the triode curves with a tracer: