That gun is a typical late 19th century Belgian import. Literally millions of them by various makers, but of the same basic pattern, were imported into the US to satisfy the demand of the growing frontier. We see them being imported well into the early 20th century, even up through the Great Depression.
There is no collector interest in these, and their value is based solely on what someone will pay for a mantle decoration (usually tops out at $200).
A very important caveat: these guns are absolutely NOT safe to shoot with any form of modern ammunition. Even if tight-as-new, these guns were not designed to handle the pressure curve of even 'low-brass' modern shells. I realize that some intrepid souls do shoot their old Belgian laminated-steel doubles with careful handloaded black-powder shells but I would not recommend even that.
The autonomic nervous system provides for involuntary muscle function - the work of breathing, digestion, and so forth. On some folks, that's a pure waste of ingenuity.