Homegrown modem from days of yore

From the MAKE: Flickr pool

Anachrocomputer shares with us this handmade piece of digital days gone by –

Top view of the 300 baud acoustically-coupled modem that I built in 1984. I made the double-sided PCB myself with an etch-resist pen (Dalo pen) and some rub-down transfers. The main chip is the Motorola MC14412V single-chip modem, but there are also some LM311 op-amps and LM324 quad op-amps. The board is normally installed inside my Compukit UK101.

That’s some well-kept shiny copper for a 25 year old board! Hmm, makes me wonder – what methods(if any) are people using to preserve their hand-etched circuits these days? – 300 baud modem, PCB