Smith's Marks on Masonry Tools

The stamp or etching on a forged tool that identifies the manufacturer and possibly the model number originated with blacksmith's identification of their work. Here is more information on smith's marks, also called forge marks, from a Belgian site: Museum for Old Techniques

"All kinds of identifying marks: symbols, letters or numbers, can often be found on tools. These marks may refer to the manufacturers..., or to the place where the piece was made.... They emphasize the quality ... or a property...; warn that there is a patent pending or in existence; record the name of the object; even give an indication of how to use it.... In addition there may also be marks of ownership or embellishment."