Well, I think that I just may have a handle on the circumstances surrounding this Emil Kerner & Sohn longarm. In West Germany in the 1960s there was a gunsmith named Helmut Kerner who subcontracted with Heym. Helmuth Kerner was the grandson of Emil Kerner and also the grandson of Imm. Meffert. I assume that there was an Emil Kerner, Senior, and an Emil Kerner, Junior. It just may be that Emil Kerner, Senior, was born in 1863 and expired in 1940. Considering that on the average a gunsmith would attain the rank of master at 23 or 24 years if he kept his nose to the grindstone. So that would suggest that in 1886 or 1887 that Emil Kerner had attained the rank of master. Sources give that Emil Kerner founded his firm and hung out his shingle in 1890. Usually at this juncture in a gunsmiths life, financial stability occurs and marriage is the next thing on the agenda followed by children. Circa 1903, Emil Kerner advertised as Aechte Suhler Jagdwaffen and retailed or was an agent(?) for Swiss maker/retailer Hermann Sasse either in Zürich or at an address of Zürich I. So if Emil Kerner, Junior was born in 1890 or 1891 he could have attained the rank of master in 1913/1914, a time when Emil Kerner & Sohn could have been founded. By 1930, ownership was with A. Schlott.
Now on to the longarm at hand after somewhat of a tangent, Imm. Meffert had some sort of close working relationship/sourcing with Heinrich Ehrhardt as many of their weapons were fitted with Ehrhardt Stahl tubes. Seeing that Heinrich Ehrhardt was from Zella Sankt Blasii, or in close proximity, I would have guessed that Heinrich Ehrhardt married one of the Meffert girls, but in fact he married Augustine Winkler in 1866. With Emil Kerner being a brother-in-law to Imm. Meffert, this reveals the reason for the Heinrich Ehrhardt stahl tubes on the Emil Kerner longarm. I would say that Emil Kerner was the wholesaler/retailer. He sourced components from his brother-in-law's firm and then sourced the work to Emil Eckoldt. When considering sourcing lines, if one doesn't really inspect family relationships, it could be a grave error in putting the overall gunmaking puzzle together. I guess the longarm to fall in the 1914-1923 period.
Kind Regards,
Raimey
rse