That is a super cool pick of JRC.. Wasn't there a Johnny Cash Guild model out there??
That's one of two custom D-60's for him, according to the Johnny Cash Museum in Nashville.
Photos here.
I'm absolutely positive I read an article in which Gruhn tells the anecdote of actually approaching Johnny to present him with a guitar (one of the prototypes?), but couldn't find it again on a search yesterday.
Seem to recall Johnny asking if he could get one in Sunburst to which George replied "Of course!" (and under his breath: "Oh thank you thank you thank you....")
Seem to recall it happened on an airplane or airport?
From that perspective I'd be willing to say that was Guild's Johnny Cash model although technically not a "signature edition" or "Hank Williams" or "Willie Porter" (Tacoma) -type model.
I'll try to found that article one more time, it's subtly humorous..