I had one back in the late 1960's, Tiny Tex, BFO model, first real detectors that I found stuff with. Gold soldered circuit boards.
Early advertisements and catalogs proclaimed they could find paper money. I don't recall them mentioning that it had to be in a metal box or jar with a metal lid.
I have some pictures of some of the later models:
My D-Tex detectors link
From what I understand Keith Wills at Broken Detectors bought out the last of their parts when D-Tex went belly up. I don't think he has any more parts to repair them.
From one of Monte's posts:
D-Tex, much like Garrett and a few other manufacturers of that era, offered detector & coil "packages" and this was the case with the RS series.
To give you an example, let me refer to the 1980 D-Tex catalog for info about these TR-Disc. and VLF/TR-Disc. models. The "series" are the TK (Treasure King), MK (Money King), CK (Coin King), SK (Search King) and RS (Relic Search).
Like Garrett, they produced detectors operating at 5 kHz and 15 kHz.