Hi Dave,
You posted 3 pictures, all about the same showing the left side of the gun.
What you have is an Ithaca Lefever single barrel break open shotgun made by the Ithaca Gun Company in Ithaca NY. They started with serial number "1" in 1927. So if it's a 3 or 4 digit serial number, you have an early one made the first year in 1927 or in 1928. Production ended on this model around 1942.
There appears to be a stock repair with that screw through the cheeks of the stock.. There is probably a crack in the stock and that screw is helping to hold the stock together.
If that is an early production gun, very likely, it has 2 1/2 inch chambers. If that's the case, do not shoot 3 inch 410 ammo in the gun. With the gun broken down, if "3 INCH CHAMBER" is marked on the barrel flats, 3 inch shells are OK.
A nice, honest original gun in decent condition with no problems would have a value around $400 -$450, maybe a little more. A cracked stock will definitely reduce the value of the gun.
Let us know if you have more questions and if you can post a couple more close up shots, that would be welcomed.
By the way, that's a very pretty pair of pants you have on there.
Jolly