6P3S-E are equivalent to 6L6 = 6L6GT = 6L6GC. Soviets cloned these several decades ago. The tubes are NOS (New Old Stock), rather vintage but in an excellent electric condition.

General characteristics:

Filament voltage, Volt: 6.3
Anode voltage, Volt: 250
1st grid voltage, Volt: -14
2nd grid voltage, Volt: 250
Filament (heater) current, mA: 880±40
Anode current, mA: 73±13
2nd grid current, mA: no more than 6
1st grid reverse current, mkA: 0.5
Cathode current, mA: -
Output power, W: no less than 5.8
Mutual conductance, mA/V: 5.2 to 6.8
Internal resistance, kOm: no more than 65
Inter electrode capacitance, pF:: 
- input: 11
- output: 6.7
- transfer: no more than 1
Operation time, h: over 5000

Limited operating values:

Filament voltage, V: 6-6.6
Anode voltage, V: 250
2nd grid voltage, V: 250
Cathode - heater voltage, V: 90 / -200
Cathode current, mA: 90
Anode dissipation, W: 20.5
2nd grid dissipation, W: 2
Resistance in 1st grid circuit, kOm: 150

Operating environmental conditions :

Acceleration of vibration loads, g: 3
- by frequencies, Hz: 5 to 300
Acceleration of multiple impacts, g: 12
Acceleration of single impact, g: 100
Continuos acceleration, g: 100
Ambient temperature, °C: -60 to +160
Relative humidity at up to 40°C, %: 98