Button, Royal Air Force?

Thirty buttons. Smooth edge. On a smooth background is a post-1901 crown, below it is a flying eagle looking right.

Object Details

ID: UNI6163
Collection: Uniforms
Type: Button
Display location: Not on display
Creator: Edward Stillwell & Son; J. R. Gaunt & Son Limited
Date made: Unknown
People: Royal Air Force; Russell, Frederick
Credit: National Maritime Museum, Greenwich, London
Measurements: Diameter: 22 mm; Diameter: 18 mm