it is a IRS bottled in bond tax seal -- when booze is made taxes are paid upon the production of the amount of booze made -- these taxed barrels of booze are sealed as they left the factory by tax agents after being 'proof tested" --to be "bottled in bond" the stuff needed to be 100 proof or better --if one bought "bottled' in bond booze --one could be sure one was getting all the bang for the buck he paid for and that the booze wasn't "watered down" -- many modern wiskeys are as weak as 80 proof ---a full 1/5 th short of 100 proof--- for every 4 barrels of "taxed' 100 proof by watering it down to 80 proof you can yeild a extra barrel of " untaxed' 80 proof booze -- the tax seals on the barrels and the paper tax strips used to seal "bonded" bottles were meant to stop the watering down of the product ( a barrel or bottle with out a proper tax seal on it is illegal booze) and thru the use of barrel tax seals and paper tax strips on bottles -- assist in stopping the selling of the "bonus' barrels and bottles gained from watering down booze on the black market -