Is there a way I can determine the date on older bottles? They aren't super old, probably the 80's at the earliest but I was curious to try to date them a little more accurately if possible. I suspect they came from seasonal gift packs from that time period. They are unopened but have no tax stamp. If they were gift packs they wouldn't likely have on on the bottle anyway would they?

Is there likely to be much difference between these older bottles and the current juice?