I can tell you when it was made with a serial number, I'd kinda like to have a look at it in the catalog as well.

It should by all rights lock itself when it closes, you shouldn't have to do it manually. Take it to a smith and have him look at it. I took my 430 O/U to my smith cause you really have to push it a long ways to the right to open it and he took it apart and said thats just the way it is but it locks up good when I close it.

Also, what model is the Sears, I bet the cross reference on it is a Savage 311.