Well, not really a fix. More an omission. Same trip to the stamp store, and the owner told me that the Hank Williams stamp had 2 major Scott catalog numbers with 2 different perforation: 10×10 and 11¼x11½.
Since I am collecting all Scott major numbers, I decided to modify the page to include Scott 2723A. The page now looks like this:
As usual, the files are on my Google Drive here: