I also recommend to open it.
I didn't drink this particular expression so far but there are wonderful oloroso matured Bunnahabhains from the 76 vintage.
In my opinion this bottle has not a big potential to increase its worth, as Bunnahabhain is mabe the least known and hyped of the Islay distilleries and this one is from an independent bottler not even an OB.
So what's the matter in collecting it?
If it's really good, you can still buy another one to collect it.