SG-3S is a voltage regulator tube. Equivalent to the 0C3, VR105/30.
Name: SG-3S;
Type: Gas stabilizer;
Cathode type: cold;
Filling: argon-neon;
Envelope: glass;
Ignition voltage, V: 127;
Stabilized voltage, V: 105-112;
Current, mA: 5,0-40;
Voltage recurrence, V: 0,5;
Ready time: 3.