You will often see references in Shugart's "bible" and other watch encyclopedea to a "5th pinion" movement. and here I will try to explain the whys and wherefores of that little demon.

Until Columbus watch co (under the control of Mr. Gruen) made the VERY FIRST successful Open Face stem winding watch, most all watches used movements that we now refer to "hunter cased", meaning the winding stem is positioned at 3 o'clock.

The "normal" wheel train for these Hunter cased watches had 4 wheels and 4 pinions that transferred the spring motor power to the escape wheel for the cyclic timing motions of the watch escapement mechanism. Along the way, the second pinion wheel drove the third wheel which also served as the seconds wheel . . and so on to the escape wheel. You can see the winding gear at the right and the third wheel in the background. So "face up" this watch winds at 3 o'clock, and the seconds chapter is at 6 o'clock.

To make life easier in the early days when a wind and set mechanism was already a serious complication beyond the Key Wind and set watches, the watchmakers made open faced watches by adding a 5th pinion to the hunter movement. This pinion which was (again) driven from the other side of the same second pinion wheel did nothing but drive the seconds hand at 6 o'clock" when the hunter movement was rotated 90 degrees in the open face case.

So I finished cleaning this transitional Illinois watch, manipulated all SIX pivot pairs into their pivot bearings on both plates and assembled it to illustrate where the 5th pinion comes out relative to the winding stem.

Makes for a purdy movement!

for an Open face watch!

That's my first look at a 5th pinion movement,Dave. Thanks.
I'm a little less ignorant today.