I was a member of Musser's "International Marimba Symphony Orchestra" and still have my King George Marimba. There were 20 20 C-C marimbas and 80 F-F. These were all tuned to A-440 instead of the A-442 of present production. This difference amounts to about one thirteenth of a semi-tone and is just barely perceptible to someone with excellent pitch (but not to me).