The following was originally published as a posting for the rec.woodworking newgroup on August 18, 1994, and is presented here with the permission of the author. The original subject title of the posting was "Black Mesquite." Kevin Riley tells me that he no longer produces caulking tools commercially, but still makes caulking mallets when requested (AWP III):

I have a small company that makes boat building tools including caulking tools. . . I make my mallets out of live oak as black mesquite is no longer imported into the US. It grows only in Argentina and Bolivia . . . The color comes with age. I have one sample of black mesquite and it is a coffee to chocolate color. They would darken with the natural varnish that was used back then. C. Drew and Co. in S. Kingston MA made the best mallets and irons in the world. I don't know if they told you why the mallet has such a funny shape. The length is for balance, and the slots in the head are to get the proper ring when you caulk a boat. The way you know that the cotton and, or oakum is made proper in the seam is the sound of the mallet striking the iron. The saying is "the mallet is alive". In the old days you could tell who was caulking the boat by the sound of the mallet. Each caulker would "tune his mallet" by adjusting the slots.