I'd be interested in seeing an image of your Keil 3-1/2. There is a paid membership website, Simon-Says.com; that has some information on Keil Nos. 0, 1, 1-1/2, 4, 4-1/2, 6, 6-1/2, 7, 7-1/2, 9, 9-1/2, 10, 10-1/2, 13, 15 & 15-1/2 but alas no 3 or 3-1/2. Note that the 1/2 suffix in Keil nomenclature denotes a key machine mounted on a board with motor whereas the lack of the 1/2 indicates the basic key machine only sans motor.

Pete Schifferli
Tonawanda, NY