Made in USA extensions. Jawco

[terrific]

That's sad.

Were they the ones actually making all the thread clean up dies and taps?

In the Project Farm video on the thread restoring sets, the sets from Lang, Gray, and CTA were made in the USA. The bolts from all three sets performed similarly, but the nuts from Lang outperformed the other two. Sadly, he did not test the files.
The Gray kit is discontinued, but the other two are still available.

I think Lang probably manufactures their own, and the other two may have been Jawco. If the CTA kit is discontinued I'll be more sure.

 

[four.cycle]

^ Yes, Lang manufacturers their own, and also supplies the same "thread restorer" tools to Snap-on.
Jawco made them for Herbrand and several other companies as well.
see here and posts following