UK: Package Sleeve for Scottish Pictorial Aerogramme, Unusual Date

This is a sleeve for a package of "50 Scottish Pictorial Aerogrammes 'Edinburgh Festival' 1987, used by McCorquodale Envelopes Limited.

Interestingly, in 1987 there was no issue of an Edingburgh festival aerogramme in 1987. This aerogramme (26 p face value, Greiner #107) was issued in 1984. The 26 p aerogramme rate was still valid in 1987, though.

So, does this point to a second issue or printing of the 1984 aerogramme in 1987 or to a printing error in the sleeve?


Reference
Greiner/Greiner, Aerogramme von Europa, 3e, 1993