The dual back-to-back "C"'s on the grips was a logo used by Charles Clement of Belgium, but there should also be other Belgian proofs on the revolver and the cylinder; you can see a smaller version of this revolver at
http://www.littlegun.info/arme%20bel...ement%20gb.htm , about 2/3's of the way down the page. If you pull the ejector pin out the front and rotate the housing out of the way, you should be able to pull the cylinder pin out the front of the frame and let the cylinder fall out the side of the frame with the loading gate.
HTH.