This is probably - together with the A. E. Dor Cognac 1811 which was the best cognac vintage of the 19th. century - the most valuable and a highly sought cognac of the famous year of the "comet".
Why? Although no manufacturer's name is specified, this cognac is perfectly documented. The best way is to read Paczensky's cognac-book (the 90s edition) on page 91 where you find this cognac at Grashoffs in Bremen (today, all bottles are sold).
But there are many Napoleonic "N" 1811, and some of them will be in trouble when it comes to the question of authenticity. The story is continued on page 123: There, we find a picture of the bottle and a price list of Grashoffs offering it at DM 6900 (that means about 3600 EUR twenty years ago!). This price was not a bargain, but it was appropriate because some time later all bottles were sold.
Now, the boom really began. Around 1998 or 1999, I was online offering almost the entire collection of Grashoff, so that some of my Russian customers had the idea to directly contact Grashoff. Shortly after that day, nearly everything was sold (and I know who bought it ;-)
Since that time, worldwide demand through Internet caused increasing prices for old vintage cognac - look at the results of auctions that time: Today you pay (in some cases) five to ten times the amount for special rarities. Prerequisite is that you can find similar bottles to verify authenticity and price level roughly - exactly applicable to that Napoleon "N", because both Paczensky and Grashoff prove its existence, and at a well known site in the UK there is another reference bottle (bad filling level) - combined with a crazy story about a Bavarian king and a letter from a grandmother to his doctor or something like that ;-) The story might be true or false (I guess it is false because I recently found this bottle at an auction in Munich, where it was sold for some thousands of euros - the letter (such a nice piece of paper ;-) surely caused one thousand extra profit.
I got the bottle from northern Germany. On the bottle, you see the embossed "N".
By the way: The producer was obviously Brugerolle, because they used the bees on the label and the crown on top for their bottles during the 19th century.