Find the LOT number on the part of the sensor where the cable splits. It contains a circle of numbers. In the middle of the circle, an arrow is pointing upwards and two numbers are written at the left and right side of the arrow. 

The LOT number of the EXG sensor, EEG-LE sensor and the SCP sensor consists of an "L" and then four digits (Lxxxx

  1. Note two numbers on either side of the arrow, these are the first two didgits of the LOT number
  2. Note the number at which the arrow is pointing to, these are the last two didgits of the LOT number

For example see the picture below. The LOT number of this sensor is: L1206.