Although not a Revenue, I would like to share this not-so-official "Semi-Official" with everyone. This stamp commemorates the 50th Anniversary of Air Mail by honoring the flight of Elliot-Fairchild Air Transport's first company flight from Haileybury Ont. to Rouyn Que. Marking the first day of use of CL#10. The commemorative stamp was allowed to grace the back of the covers that flew the anniversary flight and were officially stamped by Canada Post. So, although not given the honor of a semi-official status in references, they had their moment of fame during the flight. Perhaps one day, they will have that status. I picked up two blocks of four, two singles and also some progressive proofs of these stamps.
A contribution from Rod222 at stampcommunity.org:
Hi Steve. Attracts a Catalogue listing in "Field Guide to the Cinderella Stamps of Canada" R.G.Lafreniere. 2013 isbn 9780987804709 9 types proofs etc $5 each proof cards $10 sheet $40 Catalogue CC0620 page 28