Buried in one of the blue OM threads is a scan of my OM Walsh. I believe it is the brother of the blue one (no matter how hard I squint, I can't make the back turn blue, though
). Below are side by side scans of my card and the blue one.
There are a number of print anomalies that are identical on both cards -- a weak black border on both the right and left hand side, a red blob on the I in Chicago, and another very small red blob near his hairline above his left eye. In the image below I've circled these areas.
I believe that these similarities are reasonably strong evidence that these 2 cards were produced by the same printing plates (note that there are some other anomalies that are not shared by the 2 cards namely the small dark splotch above his collar in my card and the small red spot on the second c in Chicago on the blue back).