I got this part from an old Cornell-Dubilier AM Transceiver Mark 20
I can connect a 9V battery to it, turn the knob and the 7 segment LED switches from 1 to 40.
The only IC on this thing is an MSM5807 - PLL Frequency Synthesizer.
No BCD to 7 Segment driver IC or anything. The big rotary switch has 20 pins and seems to make a connection before it clicks.
The switch is connected directly to the LED display so I'm guessing the switch is quite specially designed.
How does this LED work?don't you hate it when you post something and realise you forgot the attachments after 15 people have already read the post