I’d be interested in seeing an image of your Keil 3-½. There is a paid membership website, Simon-Says.com; that has some information on Keil Nos. 0, 1, 1-½, 4, 4-½, 6, 6-½, 7, 7-½, 9, 9-½, 10, 10-½, 13, 15 & 15-½ but alas no 3 or 3-½. Note that the ½ suffix in Keil nomenclature denotes a key machine mounted on a board with motor whereas the lack of the ½ indicates the basic key machine only sans motor.
Pete Schifferli
Tonawanda, NY