I have a question regarding the Plank missing color: I always assumed that the light blue Plank occured because the printer ran out of blue ink, and that on the next sheet the white Plank was printed. Now I wonder if that is really what happened, because the light blue has a Sweet Cap back, but the white has a Piedmont back.
Could they still have been printed at the same time? Or would these error cards necessarily have occurred at different times? In that case what are the odds that the printers could have run out of blue ink twice at unrelated times while printing Plank, considering that so few Planks were ever produced at all?
I don't know much about the printing process, so maybe some of you who have studied this can help me. Thanks
