Re: Tell me what I have, please!
H&A made several slightly different guns using the "XL DOUBLE ACTION" name. They were made from around 1875 to 1907, in the black powder era. While H&A guns were of reasonable quality, I recommend you not shoot that gun with modern ammo.
While H&A guns are now gaining some collector interest, it is pretty much limited to a few models and to guns in like new condition. Even so, value would run about $200 tops, with average condition bringing half that.