The model number is found on the inner non switch side arm label of the hair straightener.
Heater Backing Plate For GHD Max SS5 Hair Straighteners
Heater Backing Plate For GHD Original S4C242 Hair Straightener.
"TOUCH" (C9 - T) Replacement Heater Backing Plate.
Heater Backing Plate (Used Genuine Part) For GHD Max Wide SS5.0
Cloud Nine Heater Backing Plate Fits Most C9 Models Including Touch
SiriusHair® Heater Backing Plate GHD Max Wide SS4 SS5