I have serious reservations that the dreiling is a Gesellenstück(Master Mechanic Exam piece), as Bernhard Merkel's trademark is on it. I thumbed thru Schilling makers and did not see one Gerhard Schilling but there was a firm that made/serviced barrel marking machines & the likes under the name of Schilling & Kraemer. But his name was Gebhardt Schilling. So with all that, I hazard a guess that Gerhard Schilling was a firearms merchant and not an actual maker.

Hochachtungsvoll,

Raimey
rse