Dale Ludewig
Known today as a builder of high-end acoustics, built three of these tricked-out double-cutaway 4-string electrics in the 1970s. The scale length is 14". Each pickup appears to have its own switch, volume knob, and tone knob. I'm not sure what Dale thinks about building any more of these things, but you could always ask:

Dale Ludewig
Ludewig Mandolins
1650 Pleasant St.
DeKalb, IL 60115