Cheryl, if you got a Redeye, it's a model 66...that's the only model Singer put the Redeye decals on. Redeyes are almost certainly converted if they have the motor and light....electricity was available, but not "common" until the later 20's or 30's.
Exciting stuff!! You got a GREAT deal on the 15-91, and just as good of a deal on the Redeye!
