Protected for years in its original shipping crate, this early 20th century window display advertises "Tiny Tabs Indigestion Tablets". The mechanical sign features a clockwork motor that allows the center body portion to spin and the ball on top to swing. When the swinging ball approaches the upright post on the left, the string gets caught. The ball is carried around the post, wrapping the string with it. The string then unwinds, freeing the ball, allowing it to swing again. I've seen a clock that uses a similar principle as a regulating pendulum.
From the eBay description:
Measuring 21" wide at the base by 29 1/4" tall to the top of the spinning wood balls, this early 20th century, Advertising Automaton advertises for "Tiny Tabs Indigestion Tablets." After some searching on the net I found that this product was made by the Peace Remedy Company, which was a small Brooklyn NY Company. There is very little on the net about this company never mind another advertising sign of any sort. The advertisement of a cartoon character, with a Tablet Body is very close to the "Speedy Alka Seltzer" character who came later.
The seller has a much longer description and a ton of interesting photos of the Tiny Tabs Indigestion Tablets mechanical window display.