Fernet Branca is out of Milan, Italy. They make this bitters since 1845. They still exist as of 2026. It was once marketed as a cure for various ailments, and contained opiates, as did quite a lot back then. The opiates were later removed so it could be legally sold into the US market. Today it is used as a mixer for alcoholic drinks, or in some places, mixed with Coca Cola to drink, with Argentina single-handedly consuming 75% of the production in this manner, by some estimates.
Other examples below.
Ferrari: 1 bottle frenet to 1 bottle campari. Mix both bottles, store it in the freezer ideally in a glass 1.5L bottle or pour it back into the 750mL bottles after mixing.