I read that the Xograph back was printed first, then it was switched to 1970 Xograph. After that corrections were made to cards and there was another print run using 1970 Xograph on the back.
Generally that made sense. Based on most of my variations that makes sense too. For cards with statistical changes I have one Xograph back and two different stat lines with the 1970 Xograph back. I still don't know if that is correct.
The reading also mentioned that there are five variations of cards with Xograph backs. That means they printed Xograph backs in two different print runs and 1970 Xograph backs in at least two print runs.
The 1971 Frank Howard card doesn't seem to fit into this. The correct card (1968 Washington AL) is shown with an Xograph back and the incorrect card (1968 Washington NL) has a 1970 Xograph back. The similar Felipe Alou error followed the pattern of being incorrect with the Xograph back.
Does anyone know more about this? Does anyone have other Frank Howard variations?