American colonial furniture, if it's signed at all (which most wasn't), would typically be done in graphite on a drawer bottom (most common), inside of the case (less common), or stamped into the end-grain of a drawer side (rare). There are many photos of this type of branding in antiques books, typically photographed with in the infrared to make the faded graphite stand out from the oxidized and dirtied wood background.
In my case, I prefer not to sign pieces. That drives museum curators crazy to hear, but since I'm usually making something that went out of style 250 years ago, I'm not overly concerned about someone confusing one of my reproductions from an actual antique.