In ornate letting the monogram RA&RE. Above, a Royal or Victorian crown.
This example in gilt brass, large size – 27.6mm diameter. Backmark: Firmin & Sons Ld. London.
Royal Artillery & Royal Engineers Mess Waiter’s Uniform Button ‘R.A.& R.E.’
The British & Commonwealth Military Insignia Database
Military Badges and Buttons of the British Empire and Commonwealth
This is a Mess Livery Button for the Mess at the Royal Military Academy, Woolwich, which trained officers of the Royal Artillery and Royal Engineers.