Hi Kevin,
Welcome to the forum! Wow! That is a rare marking. It's believed to stand for: III Sea Battalion Staff. The Third Sea Battalion were the German Colonial troops stationed at Kiauchau, Imperial Germany's Chinese colony. There is only one other Navy Luger with this unit marking: 1906 1st Alt. Navy #3036a. Would you mind sharing the serial number of yours?
Thanks, Norm
P.S. The last letter is a B, not an I.
|