Here is a link to the work done on the 12c issue by James Allen. It took me a while to find it and I thought it should be posted here for others to look at. Without the work done by Mr. Allen, I would not have had anything to work on for plate 3 left pane. I think that I have found most of the stamps he used for his plating efforts in Siegel auctions. But there were 3 groups that were lumped together without images. I have plated every block I found on Siegel except 2. Those two blocks are from plate 3 left pane but have no overlapping positions to locate their place.I am still hoping to find some block to connect the pieces of the left plate. Plate 3 starts on frame 7. Here is the link to Mr. Allen's work:
https://www.uspcs.org/resource-cent...f-1851-1861/