50+ year old bottle of champagne...

[Unknown]

I've recently gotten ahold of a bottle of champange my grandfather brought back from France after WWII. It's called "Monopole Red Top." It was made by Heidsieck & Co. in Reims. The only other information on the lable is the date the company was established "Maisen Fonde en 1785" and a marking in the lower right hand corner that reads "Gout Americain." There are two things, however, that really caught my eye. It still has it's original straw bundle that wraps around the bottle (I'm guessing to keep out light) and a large red diagonal marking across the lable that reads (In English and French) "Reserved for Allied Armies." There is no back lable, and no information on exactly what KIND of champagne it is. It's obviously of some value, but how much, and where would some good internet sites be to do research or find a buyer? Any help would be appreciated.
-U