I'm skeptical that this gun is circa 1911 considering it is a hammer gun, underlever with rebounding hammers.

I'm going to wager 1896-1906 on this one. Looking forward to the additional info and proof marks so we can better estimate it.

It looks like a great gun!

Raimey, isn't a Henri Roux action indicative of a rounded boxlock with internal hammers and an underlever? Whereas this gun appears to be a back-action hammergun with an underlever of a different sort. And what is the top lever used for on this gun?