I have determined that it is at the top of the presser foot shaft, where it meets the knurled knob atop the machine body, that things are fused.
I have it in the Tri Flow spa now.
Question for Steve or anyone else: Will the knurled knob ideally loosen with hand strength only? Or do you think I should ultimately loosen it, once the Tri Flow has marinated in there a while, with a grippy tool? (vice grip, or similar, cushioned with leather)
Also wondering whether there is a trick to removing the upper tension spring. Its tip is broken, and the rest of it does not want to come out of the assembly. Will this solve itself once I have freed up the presser foot shaft and am then able to lift the presser foot and thereby release the tension on the upper thread tension mechanism? Or is there another trick of which I am not aware?
The wooden base is quite badly trashed, so I am considering the most cardinal of sins, and perhaps ultimately sending it to Wood Heaven, as it is beyond my ability to restore it. Must first figure out an alternate way of holding the stitcher, as it will not rest free standing, as my more "modern" stitchers will.