? Keith Eickert Dual Tach instructions
 

Does anyone have an instruction sheet for the Keith Eickart dual tach gauge to adjust rpm settings??? It is adjustible but has no detents on the "adjuster" like you see for setting 4-6-8 cylinders. It seems to change by a ratio situation. I set it at one rpm & it seems off at another when compared to a test tach???
Help!! (I bought this from Eickert before it became the "new" K. Eickart & no instructions came with it.) Now the "new" Eickart has no information on their dual tachs.
HELP, please. :(