Having spent some time reading up on old cocktails I came across one of many intriguing cocktails in Ted Haigh's Vintage Cocktail and Spirits book. One of them immediately caught my attention for 2 reasons. Firstly, the cocktail was described needing specific measurements of a teaspoon. Suggestions were strongly mentioned in writing that coffee spoons, or just eyeballing it "wouldn't cut it". Secondly you would need one item besides gin, vermouth, and orange juice. You would need a special liqueur I have never heard of before called Parfait Amour. If you didn't measure this liqueur in the cocktail correctly, it would overpower everything.
Parfait Amour is actually a very interesting liqueur. It has a grape jelly bean quality, with marshmallows, somewhat orange-"y", and even a little licorice aftertaste. It does seem kind of well... "girly" but at 50 proof it can pack a punch. It is not to be taken lightly.
Here is how to make the great classic Jupiter cocktail based on Ted Haigh's suggestion. Try one for youself it's great.