Hmmm. Old Summicrons are notorious for tight rings. You may need to drip in some naptha to unlock the front optical head to get the front head off. Mine separates behind the two front knurled rings, and in front of the aperture dot. If it were me, I'd drip it in there.
Mind you, dripping in naptha was how I locked up a Summarit. :-(
Okay, looks like you have a project on your hands. Something has to stop the rotation of the focus helical; typically it is a single screw. Maybe that knurled ring right in front of the focus scale comes off, and uncovers a bunch of screws.
Good luck, go slowly, take notes.