The following entries appear on pp. 469-470 of the 1912 edition of “An Encyclopaedia of Freemasonry and Its Kindred Sciences” by Albert G. Mackey.
Marks of the Craft
In former times, Operative Masons, the “Steinmetzen” of Germany, were accustomed to place some mark or sign of their own invention, which, like the monogram of the painters, would seem to identify the work of each. They are to be found upon the cathedrals, churches, castles, and other stately buildings erected since the twelfth century, or a little earlier, in Germany, France, England, and Scotland. As Mr. Godwin has observed in his History in Ruins, it is curious to see that these marks are of the same character, in form, in all these different countries. They were principally crosses, triangles, and other mathematical figures, and many of them were religious symbols. Specimens taken from different buildings supply such forms as follow.

The last of these is the well-known vesica piscis, the symbol of Christ among the primitive Christians, and the last but one is the Pythagorean pentalpha. A writer in the London Times (August 13, 1835) is incorrect in stating that these marks are confined to Germany, and are to be found only since the twelfth or thirteenth centuries. More recent researches have shown that they existed in many other countries, especially in Scotland, and that they were practised by the builders of ancient times. Thus Ainsworth, in his Travels (ii., 167), tells us, in his description of the ruins of Al-Hadhv in Mesopotamia, that “every stone, not only in the chief building, but in the walls and bastions and other public monuments, when not defaced by time, is marked with a character which is for the most part either, a Chaldean letter or numeral.” M. Didron, who reported a series of observations on the subject of these Masons’ marks to the Comité Historique des Arts et Monumens of Paris, believes that he can discover in them references to distinct schools or Lodges of Masons. He divides them into two classes: those of the overseers, and those of the men who worked the stones. The marks of the first class consist of monogrammatic characters; those of the second, are of the nature of symbols, such as shoes, trowels, mallets, etc.
A correspondent of the Freemasons’ Quarterly Review states that similar marks are to be found on the stones which compose the walls of the fortress of Allahabad, which was erected in 1642, in the East Indies. “The walls,” says this writer, “are composed of large oblong blocks of red granite, and are almost everywhere covered by Masonic emblems, which evince something more than mere ornament. They are not confined to one particular spot, but are scattered over the walls of the fortress, in many places as high as thirty or forty feet from the ground. It is quite certain that thousands of stones on the walls, bearing these Masonic symbols, were carved, marked, and numbered in the quarry previous to the erection of the building.”
In the ancient buildings of England and France, these marks are to be found in great abundance. In a communication, on this subject, to the London Society of Antiquaries, Mr. Godwin states that, “in my opinion, these marks, if collected and compared might assist in connecting the various bands of operatives, who, under the protection of the Church – mystically united – spread themselves over Europe during the Middle Ages, and are known as Freemasons.” Mr. Godwin describes these marks as varying in length from two to seven inches, and as formed by a single line, slightly indented, consisting chiefly of crosses, known Masonic symbols, emblems of the Trinity and of eternity, the double triangle, trowel, square, etc.
The same writer observes that, in a conversation, in September, 1844, with a Mason at work on the Canterbury Cathedral, he “found that many Masons (all who were Freemasons) had their mystic marks handed down from generation to generation; this man had his mark from his father, and he received it from his grandfather.”
Regular Mark of the Craft
In the Mark Degree there is a certain stone which is said, in the ritual, not to have upon it the regular mark of the Craft. This expression is derived from the following tradition of the degree. At the building of the Temple, each workman placed his own mark upon his own materials, so that the workmanship of every Mason might be readily distinguished, and praise or blame be justly awarded. These marks, according to the lectures, consisted of mathematical figures, squares, angles, lines, and perpendiculars, and hence any figure of a different kind, such as a circle, would not be deemed “the regular mark of the Craft.” Of the three stones used in the Mark Degree, one is inscribed with a square and another with a plumb or perpendicular, because these were marks familiar to the Craft; but the third which is inscribed with a circle and certain hieroglyphics, was not known, and was, not, therefore, called “regular.”
The full text of the 1912 edition of Mackey’s “An Encyclopaedia of Freemasonry and Its Kindred Sciences” may be found at:
Mackey’s Encyclopaedia of Freemasonry: Volume I Mackey’s Encyclopaedia of Freemasonry: Volume II