That's the size of a UK two pence or a US quarter "BRITISH RAIL LOGO ON RED BACKGROUND". "BRITISH RAIL LOGO ON GREEN BACKGROUND".
6 x BRITISH RAILWAYS BADGES BUTTONS PINS (Size 1inch/25mm diameter) LNER LMS GWR
6 x BRITISH RAILWAYS BADGES BUTTONS PINS (Size inch/25mm diameter) LSWR GNR GWR
4 x BRITISH RAIL RAILWAYS RETRO LOGO BADGES BUTTONS PINS (1inch/25mm diameter)
4 x BRITISH RAIL RAILWAYS INTERCITY BADGES BUTTONS PINS (1inch/25mm diameter)
4 x BRITISH RAIL RAILWAYS ENTHUSIAST BADGES BUTTONS PINS (1inch/25mm diameter)
2 x BRITISH RAIL RAILWAYS RETRO LOGO PIN BADGES
