If you'd asked I would have said hers was '73 but at some point the only difference between a late '72 and a '73 is a serial number, not specs. In case you have not stumbled across the often retold story, Dan Schwartz used his hollow, and somewhat modified, M-85 on the Thursday Night Music Club sessions. Sheryl loved the sound but ended up with a solid body M-85 instead.
If you ae going for tone, and not ergonomics or appearance, there is a lot of evidence that people cannot hear the difference between a factory stock M-85-II with humbuckers and a JS-II or the same vintage.