There were 2 of the little o.f. and hunter style production lady watches. 1904-20? The early one very rare is by gruen hi q. supplier Aeby. Example here is 126989 Madretsch 1907 gift hunter. The 141185 o.f. model also rare is by Le Coultre one of the Dietrich Gruen high grade watch movements suppliers. Example here is 1914 gift open face. Photo by seller. Both in fine gold Gruen made cases. Also added serial 7000 a unique 10 1/2 ligne Gruen miniature. These 3 well represent the smallest Gruen p.w. selection.
Added (not mine) what I think is best early w.w. movement. 8 3/4 ligne size from a platinum w.w. of maybe 1925. I think movement is about a 1918 design? Notice its serial is 146644; a number sequence applied to the Dietrich Gruen high grades.