Many years ago I had a sample of Abbott's bitters run through a gas chromatograph in order to try to figure out what it's various components were, the image here is the results of that and here is a recipe based on that:
5 grams Star Anise crushed.
20 g. Bay - Pimenta Racemosa not Bay Laurel that we normaly use in cooking
40 g. Benzoin resin
40 g. Cardamon pods crushed
470 g. Clove Buds whole
16 Sticks of Cassia or Cinnamon.
6 g. Spearmint
3 g. Lavender Flowers
3 tsp. Dried Gentian
1 1/2 cup chopped ginger
14 g. ground nutmeg
8 g. allspice berrys crushed
225 g. Tonka Beans cracked
Note the 470g of clove. That is a LOT, and it is the Eugenol in the original GC that tends to imply this much clove, but personally I think that this is wrong, and the eugenol is coming from someplace else because when you use that much clove, or even half that much clove, it totally takes over the product. Many of the Abbott's recreations I've tasted so far are based on my gc, and they almost always are very clove heavy.
-Robert