I should mention that the helmet was obtained via a relative of Ullmann in 2010 in Cottbus, Germany, where I presume he was residing. Unfortunately no attempt was made at that time to follow up on the history, and I am having trouble finding any information about anyone in his age group that may have passed away in the interim in that town. Maritime Kriegsmarine maps that came with the helmet are for the Wilhelmshaven area. Thus, I suspect that the person was stationed there at some point.