One Single STC 4045A electube.  

There is another pair listed.

The 4045A is a directly heated tetrode the Type designation is of the form that indicates an STC valve. 

The valve was used by the GPO (UK General Post Office) and was there called the POVT145 

BEAUTIFUL PEAR OR EGGPLANT SHAPE. Due to age some Logo fainted. Appears Unused. Stored in other white carton. Light age wear.

Rarer Than PX25 PX4 Tube, though they share similar shape.

Likely from the 1940/50s. For potential audio amplifier project.

Last picture shown from sold item thus for reference only.

Base

Europe 5-Pin (O5A, B5)

Was used by Telephony Postal 

Filament Vf 5 Volts / If 1.6 Ampere / Direct /

250V, 60mA anode

===============Tube type: 

Screen-grid Tetrode   Audio Frequency. 

Ca. 1925 up to 1945 very rare. ***

Identical to 4045A = VT145_GPO = CV243

Base Europe 5-Pin (O5A, B5)

Amplification factor (Va=145V, Vg2=70V, Vg1=-60V)

5.2 Anode impedance (Va=145V, Vg2=70V, Vg1=-60V)

3650 ohms

Pin Function

1 Anode

2 Control grid

3 Filament +

4 Filament -

5  Screen grid