elevator

Hi, I’m new here! I recently purchased this wing section at an antique store with no accompanying information. I cannot for the life of me figure out what it belongs to. I’m pretty sure it’s an elevator, but who knows at this point. (Please disregard the excess holes and bolts, someone made this...

Can someone please tell me how to find-locate-define the center-line of a model airplane... I have spent 2 days searching for an example and all I can get is a reference to it, but no visible image or description of where it is. I assume that it's derived from the Cord Line of the airfoil...