I just took another look at it, and don't know how I missed this before, but the top was stolen from another table too. It currently has hinges on the edges like this:
But it also has old broken hinges that are not evenly spaced. They are hidden by the apron, but one of them becomes visible when the table is upside down and you swing the movable leg out:
The other old hinge is barely visible and is in totally the wrong spot for the table as it's built right now:
I love this table more and more. It's a real Frankenstein piece. It was made of bits and pieces of other table(s) a long time ago.
I also sent an e-mail to a local auction house that does assessments to see what they have to say. I'm sure they would charge for a written assessment, but I told them I might be interested in selling it, and hopefully they will give me a ballpark.