Vintage EDL Pocket Probe Thermometer Demo & Teardown

In this video I check out a vintage Pocket Probe pyrometer by Electronic Development Laboratories.
This tool is unique as it doesn't use any batteries.
We'll test it out and take a look inside, so I can attempt (and fail) at figuring out the passive circuitry that makes the instrument work.

00:00 Intro
00:47 Testing
01:36 Disassembly
02:14 What's Inside?
03:30 How the Probe Works
04:03 Reassembly