Its bare, oxidized aluminum. If you like that look, I'd leave it, but it really isnt a finish, its just a 57yr old tin boat.
FYI we love pix. Yours can possibly look any worse then several Ive dragged home, even if it has a tree growing in it.....
I like the oxidized look, but my Admiral doesnt like that it'll often leave gray/black streaks/smudges on her clothes if she rubs against it.
You could buff or polish it, but then you'll need to protect that 'new' buffed surface or it'll age back to an oxidized aluminum like it is now. Thats why I like the bare oxidized aluminum look. Low maintenance
There are several protectants forum members use
SharkHide
Sonus
Or buffing w several different polishing pads/bonnets and compounds to a high polish and keeping it cleaned and waxed