Hi, Don - I heard mentioned once some time ago that many, or maybe most, A/C paint shops used templates for laying out N numbers when refinishing. I saw a template set once at a shop that specialized in restoring Stearman and Waco airframes. They appeared to be brass, had the rolled edges for connecting in series, much like the sets all military bases used for stenciling everything.
As I recall all letters and numbers were angular, no curves, all vertically oriented. The figure "8" was composed of a series of 45 degree angles, the middle of the 8 was a 90 degree angle. A friend and I owned a '65 Comanche 250 with factory paint, those were the N number style that were on it. Then we bought a 210, it had the more modern curved numbers that you still see on Cessna's today.
For scale purposes I believe they were 12 - 14 inches high and the dimension of the line stroke was 2 inches I think. Perhaps a Google search for "Aircraft registration masks / templates / decals" would yield more info. Hope it helps.
Patrick