Vintage The St John Ambulance Association Large Cap Badge

A large sized white metal cap or sleeve badge for the St John Ambulance Association, it is of a domed shape and carries a registration number to the front of 111905, this would date it to 1889 but I think that must be its inception date, it comes in good condition and a previous owner has scratched his name on the back 'Smith', it measures just under two inches in diameter.