Sort of paraphrasing Axel E., generally speaking & from a simplistic viewpoint, Krupp delivered bar stock with Cast Steel for Rifle tubes and Fluid Steel for scattergun barrels. Anything else is just advertising that the maker put on the tube to make the end user think he was getting a better grade than run of the mill Krupp Steel. Prima Krupp Stahl is just one such example.
But the makers were supposed to have strict rules from each steel maker and apply those characters when utilizing their steel bar stock. I will search for the tube maker steel stamp rules.
Serbus,
Raimey
rse
