Canada Stamp - Christmas Seals #CS89P - Christmas Seals (1990)

Set of 7 progressive proof strips

An extremely interesting and colourful set of 7 progressive plate proofs showing how the 1990 Christmas seals came about. The lithographic ink layering process was as follows:
1) yellow
2) magenta
3) yellow & magenta (orange)
4) blue
5) blue & yellow (green)
6) blue & magenta (purple)
7) yellow, blue & magenta (orange, green & purple)