The position of the date & ledger number is undoubtedly that of Z-M. There is another set of proof marks lower on the flats, along with multiple preliminary stamps higher on the tubes(Klett or Kelber-jagged encircled K??), that have been worked off or are washing out by odd light reflection which could point to an earlier pass? Just the >>mm<< touchmarks alone date it to circa 1911. To be more in-line w/ the >>mm<< stamps, the date code might be 1909? Just need better images of the marks along the lower rib.

Ah, I use the Old English spelling of sears:

https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=270357&page=all
Keßler, O. Geyger, H. Schepring.....

Cheers,

Raimey
rse