GGCA's Axel E. kindly provided me these diagrams from Adolf Zimmer's text from 1877.







There are a couple of Teschner threads with info: http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=198557&page=1

Purely as a guess I'd say your longarm was made in the 1880s. Triggerguard bows were a bit more sculpted as a holdover from the percussion era and I for one think the Neo-Gothic period.


Kind Regards,

Raimey
rse