I also found somewhere the picture of a Remington rolling block rifle stamped with "Lebeau freres" rather than Nagant who did hold a license.
The brothers were doing all kinds of stuff, it seems.
There is some confusion on who the brothers actually were either Jules and Auguste or Jules and Gustave.
It looks to me like Auguste replaced Gustave at some point.
The late 1860s were a gold mine for Belgian weapon makers with the US civil war and the Franco-Prussian war among other markets, so it is no big surprise than the Lebeaus were in the thick of it, far away from making luxury hunting gear.
WC-