Re: Forehand Hopkins & Allen
Welcome to the forum, but can't add much to your findings. Forehand and Hopkins & Allen made good utility grade guns, but there are no serial number records. It's a black powder gun with shorter chambers than now standard, and use with current ammo would quickly loosen the lockup and possibly cause greater damage.
There's little collector interest in old standard grade shotguns, and value as a decorator will usually be less than $200.