Yeah, here's an old thread on Heinrich August Theodor Erhardt tubes:

https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=177833

And his 1893(U.S. of A.) metal vessel fabrication patent:

Nr. 495245A

https://patents.google.com/patent/US495245#v=onepage&q=&f=false



Cheers,

Raimey
rse