Button, Royal Tank Regiment?

Button. On a smooth background is a post-1901 crown above the initials which could be R. I. R?

Object Details

ID: UNI5946
Collection: Uniforms
Type: Button
Display location: Not on display
Creator: Firmin & Sons Limited
Date made: After 1901
People: Royal Naval Reserve; Captain Hennessey
Credit: National Maritime Museum, Greenwich, London
Measurements: Diameter: 18 mm