Saddles from late 1954 were the plain steel barrel type with no grooves. They were .250” in diameter. After mid 1958 the plain steel saddles were replaced by the .250” diameter threaded saddles that remained a standard part until sometime in 1968.In 1968 the .250” diameter steel saddles with the groove at each end were introduced. The groove took the diameter of the saddle down to between .215” to .220” at the bottom of the groove where the string is positioned.