6Z4 Shuguang Beijing NUEVO DE LOTE ANTIGUO Rectificador Válvula Preamplificador Little Bear T10 T11
This rectifier is a classic double diode with shared cathodes and a 6.3V / 600mA heater. Preamp valves like this double triode don't need any further setting up or baising, so thats all there is to it.