Thanks Bro. Nudge
Carnegie and Bethlehem Steel were licensed to manufacture Krupp steel plate in 1897; New York Times Nov. 7th, 1897
http://query.nytimes.com/mem/archive-free/pdf?_r=1&res=9A00E5DA123CE433A25754C0A9679D94669ED7CF If either produced Krupp marked shotgun barrels for U.S. makers (Ithaca, Fox, Baker, Meriden Fire Arms, Torkelson, Tobin) is unknown.
Krupp marked tubes also stamped “Acier Cockerill” or with “LLH” of
Laurent Lochet-Habran are commonly found.
I've not seen anything about Sanderson Brothers or Crucible having a license for Krupp, and we know that BARREL tube steel used by U.S. makers was sourced almost entirely pre-WWI from Belgium, and after a brief break, that continued after WWI.
As to Krupp's recipe; it depends on which steel
American Rifleman, April 8, 1915, Fred Adolph, “More About Gun Barrel Steel”
https://books.google.com/books?id=EpcwAQAAMAAJ&pg=PA25&lpg “Krupp makes 200 kinds of steels”
One analysis of Krupp
Fluss Stahl showed it to be AISI 1045.
The single specimen of 1898 Hunter Arms “Armor Steel” I analyzed was 1045 Carbon Steel with high Phosphorus and Sulfur = AISI 1211 Rephosphorized Resulfurized Low Alloy Steel.
Old thread but lots of Krupp infro, mostly courtesy of Bro. Raimey
http://www.doublegunshop.com/forums/ubbt...amp;type=thread 
