I had multiple fan failures which brought down my system, so instead I picked up one of these heatsink cases and it’s been running mostly uninterrupted for years.

It’s a GPO 706, which is a classic British bakelite phone from the '60s. I have it hooked up to a SIP trunk through an OBi 100. Right now it can receive calls but not make them because I haven’t gotten around to sorting out a pulse-to-tone dialing converter yet.