Came across this interesting (at least to me) webpage about the yearly postal rates and how definitions of a letter have changed over the years.
https://www.adminware.ca/checklist/chk_rate.htm
From the days of third class mail for 1 cent, local mail for 3 cents and mail that had to go beyond your local area costing 4 cents (rest of Canada and the USA).
The webpage has not been updated since 2014, but is still up to date as there have been no stamp rate changes since then (2018 rates will be the same as 2014).
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