The date code of the Supra family of headsets will be located under the ear cushion.  The first two numbers represent the month (01=January, 02=February…).  The two numbers following the dash represent the year (05=2005).  Next is the model of the headset.  An “H5″ represents the H51 model.  An “H6″ represents the H61 model.  If an “N” is present, the headset is a noise-canceling model.  Any trailing characters are used by Plantronics for coding purposes.