Canada #1027a, Canada Day 1984 Pane Of 12 On Canada Post OFDC
A Canada Post official FDC Canada Day 1984, franked with a pane of 12 stamps
Envelope fluorescence is an aspect of post-1971 FDC's that is completely ignored by all the catalogues. I'm not sure why, as FDC's after 1971 are a standardized Canada Post Product, with issue specifications - exactly the same as the stamps on them. The envelopes are but one component of this product in the same way that tagging is to a stamp, or gum is to a stamp, and in many cases you will see varied reactions under UV for FDC's that otherwise look exactly the same. To the extent I see differences I will describe them here.
Unitrade values this cover at $8.10.