[Elecraft] Is my K2 off-pitch?

[Christopher Kimball]

I'd like to set my K2 (S/N 4913) to have a sidetone pitch of tenor C on 
the musical scale. This is corresponds to a frequency of 523.251 Hz.  Of 
course the K2 sidetone is settable only in 10 Hz steps, so an exact 
match isn't possible.  Oddly, the closest I can get to tenor C is at 510 
Hz, not 530 or 520 Hz. 

I'm trying to align the filters with an XG2 RF generator and a pitch 
pipe, using Tom Hammond's, N0SS, procedure.  If this is unreasonable, 
please advise.

Chris Kimball
WB4WZR