The mark below the bore diameter stamp looks to be a jagged circle and if there is an encircled "K", it might be the mark of Louis Kelber. Is there a steel type stamp on the rifled tube? I wouldn't assume it was Witten also. What is on the butt-plate?

One might narrow the date from 1894 to 1910 if the Monopol trademark is that of Auguste Francotte:
(forced translation) of site below:

"322 N 12th of the month of October 1894 to 11 o'clock in the morning several Auguste Francotte and C Street weapons manufacturers Mont Saint Martin in Liege occur at the Registry of the Commercial Court of Liège and deposit model in triplicate Brand Which MONOPOL below indicates several Auguste Francotte and C adopt state to be affixed on firearms and weapons parts in their manufacture as well as papers and packaging business This mark represents the word Monopol It applies to flat or embossed as well as in all characters It is used in the model dimensions and in other larger or smaller"




http://books.google.com/books?id=wloMAAA...pol&f=false

Trademarks 640-646 are some of Auguste Francotte's.

A chamber cast isn't that difficult. Either purchase some Cerrosafe or melt some wax from a candle. Put a paper towel or stop about 1 inch into the rifling and fill with wax, let cool and punch out from the business end.

Kind Regards,

Raimey
rse