Re: hopkin and allen revolver worth
I believe that is the New Model Automatic Hammer Revolver, made from 1894-1907. Those made after Jan 1, 1899 are not legally antiques under Federal Law. The caliber would be either .32 Smith & Wesson (that is the name of the cartridge) or .38 S&W, but firing modern ammunition is not advised. Perhaps someone else can get the date of manufacture more closely.
The term "automatic" in the name has no connection with an automatic pistol; it means that ejection of fired cartridges was "automatic" when the gun was opened, without the need to push an ejection rod.
The gun looks to be in good shape, but even so a retail value would be around $100-120.