Coming into this many years late, interesting that I'm following another local guy in finding this stuff.
I just scored an 8 piece set of Tenadium tools, so had to do some digging to see who / when / where they existed prior.
Looks like TENADIUM was filed as a trademark in 1929 by L Michels & Söhne, Ronsdorfer Strasse, Remscheid. The document is in French, so humor Google Translate as they come up with:
L. MICHELS & SÖHNE, tool manufacturer
8-16, Ronsdorfer Strasse, REMSCHEID (Germany)
Tenadium
Screw wrenches, socket wrenches, crankshafts, pliers, dies, hammers, saws, bow saws, files, screwdrivers, chisels, center punches, center punches, punches, plane knives, cutting tools
measurement, drills.
Registered in Germany on March 1, 1928/July 16, 1928
from:
Amazingly, they seem to still be in business there,
https://web2.cylex.de/firma-home/l--michels-_-soehne-8482835.html
Looked like they advertised the Tenadium from 1929 - 1950 or so, based on Google Books.