VT-25 is the military designation for the type 10; 10Y is the uprated transmitter variant with higher plate dissipation (15W CW vs 10W for the type 10 in audio service).
Grid voltages in the RCA datasheet are referenced to the mid-point of the filament when operated on AC. If operated on DC, reduce each stated grid voltage by 5.0V and reference to the negative filament terminal.
VT-25A is a variant with oxide-coated filament instead of thoriated tungsten, drawing approximately the same heater current but with different emission characteristics. The two types are not always interchangeable.
The 1602 is a ruggedized military version; CV603 is the British military equivalent.
UX-210 and CX-310 are the original 1920s RCA and Cunningham designations respectively for the same tube in globe/balloon envelope.
Pin Layout — UX4
1Filament
2Plate
3Grid
4Filament
Socket-Compatible Tubes ⚠ Not electrically compatible