Oh, come on!
This HAS to be an engagement ring!
But knowing Clark, it won't.... He wouldn't give her a ring in a pub or in front of any witness...

And what about this girl? Does Lois really trying to mate her with Clark?

Clark: "So what are you saying? I should go crawling back on my hands and knees?"
Martha: "No, honey. Fly back. It's faster!!"