5C4S / 5U4S tube near 5Z4 = CV1863 = 5Z4GT. Old ver. glass Cobra
It is commonly assumed that the Russian 5Ц4С (5U4S) rectifier is equal to the western 5Z4G, and its true! The only difference compared to a vintage Brimar is a slightly higher peak inverse voltage at 1400v in stead of 1350v for the 5Ц4С.
All tubes new, military equipment and have "OTK" mark. Near equivalent: 5Z4, CV1863 and 5Z4GT.
Heater voltage, V: 5
Variable effective stress of the secondary winding of the transformer, V: 2х500
Resistance in the anode circuit, Ohm : 4700
Capacitor filter, uF: 5
Heater current, A: 2
The rectified current, mA: 122
The rectified current when the heater voltage 4.5 V, mA: 100
Most heater voltage, V: 5.5
The smallest heater voltage, V: 4.5
The greatest amplitude of the reverse voltage of the anode, in: 1350
The highest average value of the rectified current, mA: 125
The greatest amplitude of anode current, mA: 375
All datasheets here.