What is value of gift box of chenin blanc rose and french colombard 1978?

It is unlikely that either of the wines has any intrinsic value, in other Words they are probably undrinkable. Although chenin blanc ages well I suspect this doesn't apply to chenin rose (which must have red variety in it as well.There may be some sort of interest as historical artifacts.

If you own these I suggest you get a couple of wine loving friends around and drink the wine. have a couple of more recent wines on hand in the event (very likely) that you are disappointed. They may be quite interesting, but I doubt if anyone would pay any serious money for them.

Cheers