Actually, Krupp only provided bar stock to a mechanic who thru his craft could transform the bar stock into a rough bored tube. So it is possible I guess that the bar stock was per a Krupp recipe under license of course, but at a different facility than Essen. Now tracing the rough bored tubes would be another task entirely. But pre-WWI the bulk, if not all, were transformed by the Liege mechanics.

Cheers,

Raimey
rse