Here is a 16-bore Colleye System pinfire sporting gun retailed by August Gottlieb Schüler of Suhl, Germany. The action (and possibly the whole gun) is by Maximilien Nicolas Colleye of Liège, Belgium. The Colleye System is a single-bite pivoted underlever hinge action which, when unopened, has a strong resemblance to the Bastin action (however the barrels rotate, they don’t slide forward).
Maximilien Nicolas Colleye (also spelled Coleye and Coley; also traded as Colleye Fils) was a gunmaker/actioner located in Hoignée-Cheratte, Liège, in business from 1850-1865. He was the son of well-known gunmaker-inventor Henri Joseph Colleye. The Colleye mechanism was apparently popular in Germany, and several large gunmaking firms such as August Schuler of Suhl and Johann Peterlongo of Innsbruck offerred System Colleye guns (Peterlongo had a System Colleye gun on display at the Paris World Fair in 1867).