[87] Extensive research has been conducted by Colonial Williamsburg, Inc., on the forms of vehicles used by such Virginians as Mercer and his contemporaries.
Hogsheads and casks of tobacco were branded with the symbols or initials of the original owners. Many of the brands are recorded explicitly in the ledger. Mercer, at the beginning of his career, used a symbol M. As his plantations multiplied, however, three symbols were adopted, based on his own two initials. Tobacco casks from Bull Run were marked I^[B.]M. Those from Sumner's Quarters bore the brand I^[S.]M, while the "Home Plantation" at Marlborough had casks marked I^[C.]M (fig. 8).
The interpretation of these symbols warrants some digression. In the 17th century, and indeed in the 18th century also, the triangular cipher to indicate the initials of man and wife was commonly used to mark silver, pewter, china, delftware, linens, and other objects needing owners' identifications. The common surname initial was placed at the top, the husband's first-name initial at the lower left, and the wife's at the lower right. This arrangement was used consistently in the 17th century. In the 18th century, however, variations began to appear in the colonies, although not, apparently, in England. Silver made in New York and Philadelphia during the 1700's presents the initials reading from left to right, with the husband's at the lower left, the wife's at top center, and the surname initial at the lower right. The large keystone of the Carlyle house in Alexandria, built in 1751, bears a triangular arrangement of John and Sarah Carlyle's initials: J^[S.]C.[88]
Like Carlyle, Mercer used initials in this fashion, but also, as we have seen, in two other combinations in which "J. M." remains constant, the upper center initial having a subordinate significance. "S" signifies Sumner's Quarters, and "B," Bull Run Quarters. "C" on seals and brands having to do with Marlborough apparently refers to Catherine, honoring her as Mercer's wife and mistress of the home plantation. The possibility that "C" stands for Cave's warehouse may be dismissed as being inconsistent with the other two marks, the tobacco from Sumner's Quarters having also been shipped through Cave's, and that from Bull Run Quarters having been stored at the Occaquan warehouse.[89]