NOTE: The PS-6600 and PS-6600 ST will use one of two possible procedures for calibration. The serial number will determine which procedure to use. The serial number label is located on the backside of the display console and the underside of the platform. Towards the middle of the serial number is a letter code. If your scale contains a letter code of "PSA", "PSB", or "PSC", your scale has internal calibration and uses the same calibration procedure. If the serial number contains the designation "PSD", your scale has 'push button' calibration and will use a different procedure. Click on the appropriate link below to view the calibration instructions for your scale.