Help Needed on 1979 G.H Mumm Champagne!

[spapadop]

Hello All,

Any help would be highly appreciated! I have no knowledge about wines or champagnes, but recently I found a bottle of 1979 G.H Mumm Rene Lalou Champagne. I am pretty sure that this bottle was not stored horizontally nor in an underground cellar. Do you believe there is any value to this bottle? Should I open it and what it tastes like? Should I try to sell it? Storing a bottle like this upright for years, destroys the taste, or even makes it dangerous for someone drink? I am not sure if I should keep it or pass it on to someone else...

Any advise is highly appreciated!!

Thanks a lot,

Stratis