First heard this song 33 years ago. Was known then as Seth Davy. Heard the Spinners do it in October '66 at a "freshers" concert at the college I attended. My recollection was that some of their words were different. Most significantly there were, according to them no strings. Seth Davy sat astride a plank on a packing case and with one end anchored underneath his bum; the free end was thus able to vibrate when the plank was drummed by his fingers. His dolls were on the end of wooden sticks and were held either under his armpit or in the hand that was not doing the drumming so that their feet just touched the plank. The legs of the dolls were "loose coupled" so that the drumming of the plank made them dance. A few years ago I did try the system of getting some very crude dolls to dance in this fashion and it worked well. Unfortunately not having four arms and hands I found I could not play guitar, sing the song and do the demonstration of the dancing dolls at the same time.
The date of Seth Davy's death was given as 1905 and in the Spinners version of the song, "the 3 dancing dolls in a jowler bin ended and the plank went to mend a back door". I would take issue with the chords given the relative minor to the key should figure as shopuld the relative minor to the sub dominant vis Am & Dm in the key of C.