The flaw in the argument above is that Nadar is the name of the Distributor/seller of the camera rather than the name of the camera's owner unfortunately. Secondly the condition isn't good enough to have a very high collectors value.
It's still going to be worth somewhere over £100/120 euros but even very good condition camera's of similar vintage often only sell for £200 - £400
Some of the websites don't show just long some these tailboard cameras were being manufactured, Sands, Hunter & Co were still making one in the late 1920's as were Adams & Co. In the case of Adams the "Challenge" of 1928 is the same as the 1882 model, the 1928 De-Luxe Universal Sands, Hunter model has a rising front.
Sands, Hunter were more of a distributor & retailer than a manufacturer so it's likely the camera was made by another workshop. Louis Gandolfi worked for Lejeune & Perken who didn't sell cameras under their own name, and the Gandolfi tailboard cameras were quite similar to the later Sands, Hunter model.