The Vintage Cognac is one of the pawn items in The Angel of Darkness. It's first found in the level Margot Carvier's Apartment. It's described as "Rare Vintage 1851" in the inventory.  Overall there are three of these bottles in the game. If they are brought to the Pawnshop before Rennes is killed, they are worth €320 each.
Vintage Cognac Locations
- Level: Margot Carvier's Apartment, in the kitchen, near the sink
- Level: The Serpent Rouge, in the cellar of the nightclub
- Level: The Serpent Rouge, behind the bar
- In-game inventory