Quote from producer's website:

BOGART’S BITTERS can arguably 
be said to have started the cocktail movement
 as it was the first ever mentioned bitters in 
the very first cocktail book published in 
1862, written by the most famous bartender
 of those days, Jerry Thomas – a name, synonymous
 with the first golden age of the
 cocktail.

Although no bottles of the Jerry Thomas
 era ever surfaced, the common belief is that
 Bogart’s was a kind of misspelling of Boker’s 
Bitters at that time. Still the impact for 
the development of the cocktail is without
 question. Before other bitters appeared in cocktail
 recipes around the world, there was Bogart’s/
Boker’s.
 A beautifully balanced and versatile
 cocktail bitter, it was even called for by
 name in the first Martini recipe, printed in
 1888, where one was instructed to use “genuine”
 Bogart’s/Boker’s, indicating that this most
 popular bitters had weak imitations floating
 around.

And this makes sense, for if one actually 
tasted one of the very few remaining bottles of original Bogart’s/Boker’s bitters, they 
would discover that this magnificent bitter
 is not a cardamom bomb, but rather a beautiful
 mix of dark spice and chocolatey coffee,
 that can only be achieved by using a very 
expensive herb, an ingredient that others 
use sparingly due to cost, but also to the 
detriment of the final product.

The Bitter Truth have spent much time
 in investigating the subject over the last 10
 years and is in the possession of a super rare 
original bottle – one of the only known bottles
 to have survived with genuine remaining 
contents, bottled around 1900.

Originally sold in iconic “lady leg” bottles
 made of brown glass, these bottles were 
defunct for about a century and have now
 been reproduced for this special edition.
 The same goes for the labels, which have
 been redesigned from this surviving bottle.
 The formula has been analysed, interpreted 
and changes in flavor profile, due to
 age, were substracted and the liquid formulated
 in the way it authentically resembles
 Jerry Thomas’ favorite bitters of more than 
a century ago.