Investing In Canadian Stamps

Certainly currency fluctuations matter, but if you want to take advantage of that (and can guess which way they are going to move), there are better ways of investing in currencies than using stamps.

As for "The price you pay will be a fraction of catalog, but since that ratio to catalog is fairly constant, the appreciation percentage is the same", that (constant ratio) may be true over a short time, but is much less of a certainty over a longer time period.

Canada first started intaglio dry printing postage stamps on pregummed paper in the early 1920's. The U.S. first started similarly in the mid 1950's.