Here is the eBay Hakko 191 guts, its very likely counterfeit. A give away is if the date code on the PCB is correct, it was made in 2/11 and this product was discontinued by Hakko in 2006. There is no Hakko marks anywhere.
As you see, its fairly simple internally, and the thermocouple wires are simply connected between red and blue. The third wire is probably just mechanical support. However, for $10, building this yourself from a kit and carving the box will cost more than $10, plus paying $20 for real Hakko sensors or $5 for fake ones.
![](https://lh6.googleusercontent.com/-vkJeqqSgNK0/TkKGG2x4F2I/AAAAAAAAAX8/YfMiCIKoKVo/s912/2011-08-09_11-17-01_885.jpg)
![](https://lh5.googleusercontent.com/-gqlk5JfDnho/TkKGDpoM-pI/AAAAAAAAAX4/y4lwelQ4gvI/s912/2011-08-09_11-21-19_774.jpg)
Looks real enough, but I've never seen the true version:
![](https://lh5.googleusercontent.com/-4gXWLnF50iU/TkKF7L4264I/AAAAAAAAAXw/NQITMctwRqM/s912/2011-08-09_11-24-52_563.jpg)
Copy? Down to serial numbers and Made in Japan:
![](https://www.eevblog.com/forum/index.php?action=dlattach;topic=4208.0;attach=12739;image)