I think the name to be typical for Ed. Kettner's offerings in Kln for the period & it may be that a craftsman @ Sauer applied it. Sauer & Sohn Nr. 34521 as found in Cate's text is similar in adornment. Again, during this period Ed. Kettner heavily sourced Sauer & may have performed some tasks in-house like adding a new tubeset, etc. after sourcing it from Suhl.

Cheers,

Raimey
rse