When I was a young boy back in the 1950's an uncle gave me a single shot stevens break open single shot 410. It was all metal, had no safety, I don't remember if it even had a half cock. The uncle had the chamber bored out a little longer so it would take the longer 410 shells--maybe 3" instead of only 2 1/2 ", I am not sure of the lengths. I lived on a farm and shot a lot of squirrels with that old shotgun. My oldest son has it now, I doubt if it will ever be shot again.
I hope you can find the trigger guard, that is too nice of an old gun not to be usable.