There are a great many different H&R top break revolver models, but you would probably have better luck on another forum as most members here are S&W fans. In general, most H&R revolvers have little monetary value unless they are in nearly factory-new condition.
You might try googling (or binging or whatever) "H&R Automatic Ejecting 38 S&W Caliber" as these were known, and you'll get some hits on an appropriate forum. All I know is that if it has the caliber marked on the side of the barrel it should be safe for modern .38 S&W ammo if mechanically sound otherwise. I've got an older 1890's vintage H&R which is a black powder gun.