Assuming this is a pump gun this is a variation of the High Standard Flite King shotgun. HS made several variations of police and riot shotguns. There were variations with rifle sights or bead sights, different barrel lengths and magazine capacities. Some also came equipped with bayonet lugs.
If you use the search engine at the top of the page I believe the HS was discussed in the past.
For more information see The World's Fighting Shotguns by Thomas F. Swearengen. The book is somewhat dated but the information is incomparable.
Can't help on price.
