How can you tell the difference between Scott 731 and 767?

Answer 1

Multiple 25-stamp panes were printed on a single large sheet and then cut into individual commemorative panes. The spacing (gutters) between the 767 panes is noticeably lager than between those on the 731 sheet. However, once they are cut, it is almost impossible to tell which is which. For that reason, many collectors collect "gutter blocks" of the 766 and 767 issues rather than the full panes. A gutter block has the corner stamps from 4 panes of the large sheet, showing the wider gutters in the form of a cross between them. (It looks like 4 houses sitting on the corners of two wide intersecting streets.) EBay, among other sources, often has gutter blocks listed.