That's the size of a UK two pence or a US quarter.
Piano Bench of Classical Music : Piano Solos by various classical composers.
ROMANTIC CLASSICAL COMPOSERS BADGE BUTTON PIN SET (Size is 1inch/25mm diameter)
LUDWIG VAN BEETHOVEN BADGE BUTTON PIN (1inch/25mm diameter) CLASSICAL MUSIC
JOHANN SEBASTIAN BACH BADGE BUTTON PIN (1inch/25mm diameter) CLASSICAL MUSIC
WOLFGANG AMADEUS MOZART BADGE BUTTON PIN (1inch/25mm diameter) CLASSICAL MUSIC
JOSEPH HAYDN BADGE BUTTON PIN (Size is 1inch/25mm diameter) CLASSICAL MUSIC
