It's Webb's 8th Edition (2019) #LS12 Ontario with the incorrect spelling of "Poste". The corrected version "Postes" is #A24. Value is $2.50, issued 1973. There are 24 domestogrammes in this series. #LS3-14 with incorrect spellings of "Poste" and "North West Territories, and #LS15-26 corrected in 1974. There are 24 similar 15¢ aerogrammes with the same problems and solutions. These were not affected by Webb's numbering changes..
The domestogrammes were issued as a set of 12 (showing the flower of each province and the Northwest Territories) in 1973. They were sold as a packaged of six. In 1974 they were re-issued to correct the "Postage/Poste" error below the stamp changing it to the correct "Postage/Postes". Webb's value for any of either issue is $2.50 unused. Used, any of the first issue is valued at $25.00 and $30.00 for the 1974 issue. They were never popular with the public.
Thanks everyone for the feedback. I do have the 2019 Unitrade catalogue but was unable to find my item until its location was pointed out to me. I guess I was expecting more images since it is a 'specialized' catalogue.