I just happened upon this description of a colour process, not sure exactly what it is, and it probably isn't very useful nowadays: Autotype Trichrome Carbro (http://www.oldandsold.com/articles21/color-photography-3.shtml). Is it some Carbon printing process?

Basically, it is like a cross between carbon and dye transfer in which 3 colored pigment sheets are used to transfer images from separation negatives onto a reciever sheet.

PE