5C4M / 5U4M tube near 5Z4 = CV186. Dual channel kenotron
All tubes new, military equipment and have "OTK" mark. Near equivalent: 5Z4 and CV186.
Type: double-anode rectifier
Application: alternative current rectification
Cathode type: oxide,indirect heating
Filament voltage,V: 5
Filament current,A: 1,8-2,2
Anode voltage,V: 50
Anode current,A: 0,3
Socket type: rsh5-1
Max.reverse anode voltage,kV: 1,35
All datasheets here.