E446 (Philips Miniwatt) = H4128D = RENS1284 = WE24 - vacuum pentode. Very good (at least 130% nominal emission). In details, for Uf = 4V, Ua = 200V, Ug1 = -2V, Ug2 = 100V, Ia = 4.0mA (100% Ia = 3.0mA). Measured on ELPO P-508 tube tester.