That the sign þ which appears in Greek legends on the Kushan coinage and on that of two earlier rulers has the value sh was remarked in 1872 by Cunningham, who thought that the sign was a peculiar form of Rho. In 1887 Sir A. Stein put forward the theory that it was a revival of the obsolete Greek letter San (which had the value sh), since the oldest minuscule form of San resembles, though apparently it is not identical with, the þ sign on the Kushan coinage. This has raised a good deal of discussion; on the one hand, various other origins have been suggested for the þ sign, including the Aramaean Tsade, and on the other, much learning has been expended in an attempt to show that this sign had not the value sh at all but the value r (Rho), while Professor F. W. Thomas has taken the view, which resembles Cunningham's, that the sh sign þ was derived from the r sign Á (Rho), and has also said that after the fifth century San only survived as a numeral (and as a numeral it cannot come in question, for it was written with a totally different sign). But I have never seen the one enlightening Greek text on the subject quoted.