Just going through a recent collection purchase of assorted stamps and found an envelope of corner and inscription blocks. This was amongst a bunch of other corner blocks. It is an unusual item as the stamp was printed in two colors only. Green and brown. Since green is a color combination of blue and yellow, is it plausable that the yellow was running low during printing. It is not a constant variety.
Plate corner block of four with no gum disturbance! It is a Canadian issue to celebrate the 8th International Boy Scout Jamboree held at Niagra on the Lake in Ontario in 1955.

Edit: cropped image of extra distracting unneeded clutter.