Maker's Name: 
Where made: 
9 × 7 × 7.2 cm

The transformer was used for interstage coupling between valves that amplified AF signals in a 1920's radio receiver. The turns ratio is 1:3.5 so there was a voltage gain of 3.5 between stages to boost the overall AF amplification. Valves in the 1920's were mostly triodes with typical amplification factors of 8 to 16.

The transformer also acted as an impedance match between stages, here a factor of 12. With a grid leak resistor of 1 MegOhm in the following stage, the apparent anode load resistance on the previous stage was 8300 Ohms.