This is what we call a clue.
Neuman Brothers was a Belgian gunmaking company from 1863-1924. It looks like they then merged with Clement and were in business until at least 1954.
The gun was probably made for sale in England or the USA because it is marked Neuman Bros instead of Neuman Freres.
The thread is 1670 days old because you tagged onto an old one about a Steyr pistol instead of starting your own. I just stumbled across it because I am more interested in a Steyr pistol than a shotgun.
You shoud think twice about having fun shooting a gun that old. It may have Damascus barrels and probably has shorter chambers than we make shells for now. It might be dangerous.