[P/O W. 'Moggy' Cattermole]

and the note is covering the damage sustained during a brief dogfight with a 109?
.

By 'note', do you mean the yellow diamond? That's a gas-detection panel, a piece of fabric soaked in a chemical that would change colour if gas was detected. Common on 1940 Spitfires and Hurricanes.

i was only joking that it looked like a post-it note