Please list all the markings on the shotgun. Harrington & Richardson were producing hammerLESS double shotguns as far back as 1882. sales@countrygunsmith.net
There is one for each barrel. The back one is for the left hand barrel and the front is for the right hand barrel.
If it is a fully functional (have it checked by an experienced gunsmith) gun with fluid steel barrels, back hammers or hammerless, it should bring $200+ as a shooter. If it has side hammers and twist steel barrels, it's worth $125-$150 as a mantle decoration.
The back one is for the left hand barrel and the front is for the right hand barrel.
The hammers need to be in the cocked position for the barrel set to close. You will need to insert a tool and lift the cocking piece from the front of the action below the breechface or remove the stock and manually cock the hammers in order to get the barrel set back on. sales@countrygunsmith.net
as your looking down the gun, the gauge should be stamped on the left barrel back by the stock.
There is no "break in" shotgun. A "break open" shotgun is a single barrel, double barrel, or combination rifle/shotgun which breaks open in the sense that a lever will unlock the action, allowing the barrel to pivot at a hinge at the front of the receiver, pivoting the rear of the barrel up to expose the chamber. A shells may be loaded into the chamber and the barrel pivoted back to close the action. The act to "break in" a shotgun means to fire it a few times to loosen it up.
Are the hammers on the back of the lock or on the sides? The first is probably a shooter worth $100 - $200 depending on condition. The second is a wall decoration with about the same value.
If you have to ask how to put a shotgun back together you shouldn't be touching it! Dont touch some thing that will kill you if you get it wrong.
If it is a typical Stevens double or single barrel there should be a metal lever towards the back of the stock slide it left or right and tilt the barrel down.
you pull the trigger back all the way
Look at the back of the breech. If there isn't a hammer, it's hammerless. Hammers are those things that stick up at the back of the barrel. On a single action gun you have to cock them (pull them back) before you pull the trigger. Pulling the trigger cocks and releases the hammers on a double action. All the firing mechanism is inside a hammerless gun.