Hard to tell without actually seeing the gun, but I think that derringer has a cracked hinge. Those guns were made of cast iron and Remington never changed the material even as late as 1935. The hinges didn't crack from firing, though, but from "flipping" the gun open, when the momentum of the heavy barrel block stressed the hinge.
Sadly, none of those guns has much monetary value, though I am sure your children will treasure them as you do, for the family association.
Jim