My first modem, also around that time was... 10 Dutch guilders (around $4.50 at that time). That's 'cause I bought a suspiciously modem-looking (markings, phone line transformer, line relay, etc.) full-size rack-mount board at a swap meet, no documentation on the thing, bunch of switches and leds on the front, S100-like connector on the back, 'sold for parts'. I traced the circuitry, managed to work out its intricacies, figured out what voltage it needed to work, powered it up and started experimenting. After a few days I had it worked out, created an interface to my C-64 to run the thing through the user port - with pulse auto-dial! - and built ye olde wooden enclosure with built-in power supply and a single-slot rack mount for the thing. It worked for years and was my first way to get online with that machine. It was the classiest modem I ever had, bar none.

I wonder what that board was originally used for, it was quite an elaborate thing, a half-size board sandwiched on top of a full-sized one, a bunch of expensive-looking white ceramic gold-capped circuits on the top board, the bottom one full of discrete components. It must have been something serious and expensive. Still, I suspect the C-64 I ended up connecting it to may have had more computing power than the original host.