What is the value of a W Richard 12 gauge double barrel?

Unfortunately, not very high. The name W. Richards was used on inexpensive shotguns, attempting to 'tag along" with the name Westley Richards. While Westley Richards gun were very high dollar guns, the W. Richards were not.
There was a well respected English gun maker named Westley Richards that made very nice, high dollar firearms. Unfortunately you do not have one. W. Richards was an attempt to cash in on the name of Westley Richards. They were inexpensive firearms, mostly made in Belgium. Values vary depending on condition, but most are in the $100 range.