A great russian pentode valve similar to 4P1L, but with indirectly heated cathode. You can check the valve specifications here.
I tested transconductance in left-handed triode mode: Gm=9.6mA/V @ Va=150V, Ia=50mA , Vg=-5.6V.
Here are the curves for this valve:
For the ones who want to test the SPICE model here is my take on it:
You can try the model and please let me know your results! You can always email me