You might be able to determine how old it is if you can track down when key tabs were discontinued as opposed to pull tab cans. It is certainly a can, not a round paper carton, or a plastic tub, so I would guess before the early eighties. Metal tobacco tins fell out of use in Canada around that time and were replaced by plastic tubs for RYO tobaccos. Screw top lids were common in the 60's to the 80's, I would hazard a guess your tin predates that. Was there any pricing or duty marking on it? That would help you narrow down the era.
I have also heard that H&H was once a richer, less flavoured tobacco so I am pleased to hear that is your experience of it. I first had H&H in '93 and It was more or less in its current formulation then, a definite flavour of Anise/Cardamom.
PS: I would certainly save the can after you are done with it. A great piece of tobacco memorabilia, especially in its condition. I checked a few antique sites in a brief search, several offer free appraisals if you're willing to send them a picture. They might not give you a definite year of manufacture but they should be able to give you a general idea of the decade the tin type was in common use.