For a sauce that has existed in some form or another since 1862, A.1. has a pretty unsurprising list of ingredients, with a few exceptions. Notable among them is raisin paste, H.W. Brand's stroke of genius that has been used in other sauces and prepared foods ever since. The antioxidants in raisins helped slow the decay of beef in the days before refrigeration, but also helped mask the taste of decaying beef. Apparently, even kings weren't too regal to not eat some funky steak in the 1860's.