U.S. #767 Federal Building 3c Souvenir Sheet Mint No Gum

U.S. #767 3c Chicago Century of Progress Souvenir Sheet Mint No Gum
Farley Souvenir Sheet from sheet of 9 panes
Showgard Mount Size: SGAB (Mounts for issues up to 1975, except the White Plains, in one packet)

There is no distinction between the #730 and the #766 in the sheet of 25 format. Per the Scott Catalog, “Positive identification is by blocks or pairs showing wide gutters between stamps. These wide gutters occur only on Nos. 766-767 and measure, horizontally, 13mm on Nos. 766-67; 16mm"