Can you show a picture of each entire side of the backbox and cabinet, and the full front, to show the artwork?

Look for a small serial number stamped into the cabinet front, or maybe elsewhere.

Where did the owner hear what he told you? How long had he owned this? How did it get from the Gottlieb family owner to him?

There supposedly was a modified "Dancing Dolls" produced by Gottlieb (according to the ipdb). It was an experimental add-a-ball machine.
Oddly, your machine has starburst bumper caps on it which came out much later.
I've seen some woodrail games dropped into metal rail cabinets before, but if this is the real deal, you might have something there.

I believe the material you are quoting refers to "Flipper", and not "Dancing Dolls". "Flipper" was the first wedgehead, first production add-a-ball game, and the first Gottlieb metal rail game. I've seen several in their original woodrail cabinets, and the cabinet artwork is similar to "Square Head" as is stated in the article you're quoting.

It could also be that your lower cabinet is actually a woodrail cabinet that had an aftermarket metal rail kit installed. The way the woodrailed lightbox is installed suggests that the lower box is a modified woodrail cabinet.
I've seen these metal rails tacked onto some of the later woodrail titles. It was likely done by operators in an effort to "modernize" their older stock once the metal rails games started appearing.
The cabinet paint and serial number don't appear to be factory original, but obviously were done long ago.

Nonetheless, a great find. I wish I were closer. BTW, "Dancing Dolls" was the last Gottlieb game to use lamp display scoring. All EMs to follow used score reels.

Probably another attempt to modernize the look of the game. This suggests that the game may have been operated into the mid sixties or later.

Elevatorman, are you gone now? Did I miss you by only a few minutes?

I searched for your serial number 29754 on the IPSND.net and the closest I found was 29755 for Gottlieb's 1960 Kewpie Doll which came out a few months after Dancing Doll:

http://www.ipsnd.net/details.aspx?id=3245

This number 29755 is from the old Pinball Pasture website. I have their data to corroborate this. So that is the nearest number *above* yours. The nearest number *below* yours is F29620, also Kewpie Doll:

http://www.ipsnd.net/details.aspx?id=43002

So, I'd say you have a Kewpie Doll lower cabinet.

Here is a picture of the Kewpie Doll cabinet side, a woodrail:

https://www.ipdb.org/showpic.pl?id=1358&picno=23902

Interestingly, the 1960 game Flipper, where production switched from wood rail to metal rail, was the next game to come out after Kewpie Doll.

Gee, in support of the former owner's story, if this was Gottlieb's experimentation for a new metal side rail, it fits that they'd do it on a game closely preceding Flipper. But, why wouldn't they just do it to an empty cabinet? Or, if they wanted to see how it would look in general, why not just use the fully equipped Kewpie Doll production game that would already be inside that 29754 cabinet? Why insert a Dancing Doll playfield (and backbox innards) into a Kewpie Doll cabinet? Three production games came out in the few months between Dancing Dolls and Kewpie Doll: Captain Kidd, Spot-A-Card, and Melody Lane. Why Dancing Dolls?

Well, maybe the Gottlieb executive who took this home to his kids preferred the game Dancing Dolls.

These are speculations. I'd like to hear the details from the former owner, but maybe that opportunity has passed?

Your metal side rails are wider than what Gottlieb used, once they went to metal side rails in production, shown here:

https://www.ipdb.org/showpic.pl?id=891&picno=54537

The Gottlieb production metal rails curve around the flipper button. Your rails do not curve but have a straight edge at this end, and they each are nailed down at this end with three nails that, to my eye, do not have symmetry when you compare one side to the other. Is this operator's installation imperfection, or factory experimentation?

Your metal rail on the left side, where it ends under the backbox, looks like a squared cut, while the right rail ending under the backbox looks like its cut an an angle. Am I seeing this correctly?

Can you post a picture of the full cabinet front? Also, do the inside walls of your backbox have any paper tags affixed to them, and what do these tags say, and how are they affixed?

Thank you.

When did Gottlieb stop stamping the game title initials after the serial number? My '57 "Royal Flush" still had "RF" stamped at the end of it's serial number.

$600 for all? What else did you get?