I've been going through my late grandmothers photo albums and found two photos of what I believe is a Grumman Hellcat piloted by my grandfather W. Guy Batham RNVR of FAA 885 Squadron. These will have been taken while HMS Ruler was in the Clyde before she sailed to Sydney. Can anyone help me with the handwritten number on the back of the photos. Are these the aircrafts identifying serial numbers?