Your side-by-side shotgun bearing the words 'Real Twist' is likely a common store-bought gun made in Belgium or England by the tens of thousand, and sold by such worthies as Sears, Roebuck Inc for as little at five bucks, and sometimes, depending on the maker, up to as much as twenty bucks.
Not trying to disappoint you, Sir, just preparing you for the likelihood, is all. The middle end of the 19thC and well into the 20thC was the heyday of this kind of gun, than probably put more food on the table of pioneer Americans that any food store of the day.
As for markings, I'm betting a pound to a pinch of parrot poop that it has plenty of 'em, you're just not looking in the right places. If you can take the barrel out of the wood, look underneath at the breech end - likely you'll see an ELG in an oval or similar, with lots of figures and stuff. Tell us what they say, and we can offer you a possible 'date within x years...'
We'd love to see your pics, if you can send them to somebody here who can put them up for you. After many years on this great forum, I still can't do it.
And Welcome, too!
tac