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 the early eighties. Metal tobacco tins fell out of use in Canada around that time and were replaced by plastic tubs for RYO tobaccos. Pipe tobacco may not have even been available in anything larger than a pouch after that unless you brought it over the border from the US. 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.