Heinrich August Theodor Erhardt's name has surfaced again and I think either one or both of these patents to be his tube making process, possibly for artillery only??:

http://www.google.com/patents?id=S2x2AAA...;q=&f=false

http://www.google.com/patents?id=do5EAAA...;q=&f=false

He had many patents, may be 130+, on devices associated with steel forming/making and originally was of Düsseldorf. I think Meffert sourced him or they had some relationship and I'm pretty sure he was listed in the early 1900s Zella Saint Blasii phone directory. I'm guessing he was born circa 1840 and died in 1928.

1938/1941 patent based on "Ehrhardt method": http://www.google.com/patents?id=cyhiAAA...;q=&f=false

Kind Regards,

Raimey
rse