No, not the bourbon. Craftsman sometimes use a mark to identify their work like a silversmith's hallmark, a trademark, merchant mark, or cattle ranch brand. Garret Hack signs his work in Morse Code; others use their initials, signature, a coin, or just stickers. Not wanting to be left out I pondered a bit then decided on this:
Those are my initials, RAM, in Ogham, the ancient Irish alphabet of the druids. Sometimes called the Tree Alphabet because many characters were named after trees, birch, alder, willow, etc. Ogham is written on a line either vertically or horizontally and sometimes even on circles or squares. The arrows (feathers) are the beginning and end of lines. Five slashes = R, notch = A, one slash = M. It's simple and can be adapted to different shapes and sizes.
An English to Ogham transliterator
More information on Ogham: