This is very likely a standard issue from the brand, although it is an older edition. Standard practice was to give each release a vintage, but they recently (in the last couple years, I believe) have gone over to consolidating their product as Knappogue Castle 12-Year.
The upside: the vintage editions such as yours are becoming a bit harder to find. I would guess -- and I stress that it is a guess -- you might be able to fetch about $55 for this. That's about what I would pay if I saw it for **** on a shelf locally. By way of comparison, earlier this year I paid about $42 for the bottle of 12-Year I have on my shelf right now.