Thanks, Opelfruit, for the helpful response. Here's a photo:
It's very similar to the Signatory Port Ellen you linked to, except I have a paper can, the wording on the label is slightly different, and there's the extra year of age (as you pointed out).
If it's helpful to anyone, the data on the label is:
Distilled 20.1.83, Bottled 11.96
Butt No. 25, Bottle No. 33 (hand-numbered) of 630.