Criteria for obtaining a souvenir for the Canadian provinces and territories are relatively simple: You need to have a logged find on a cache in that province or territory. There may be some exclusions (travelling caches, armchair virtuals, Locationless caches, etc.) but generally, one single find should do.
I imagine it will be similar criteria-wise once the next Canadian souvenirs are rolled out.
Thanks, we look forward to seeing other souviners soon.