Old wine from Toussaint

 is a quest item in that can be bought from Aeramas' Shop in Novigrad. It's needed for the quest It Takes Three to Tango.

This item appears to re-stock on occasion in the merchant's shop, even past the point of when the associated quest happens. As it's still considered a quest item, there's no way to drop it without using cheats, so it's best to avoid buying it unless you need it for the quest.

Associated quest

 * It Takes Three to Tango