WW1 His Majesty's New Zealand Transports on war service badge

A scarce original Great War official 'On War Service H.M.N.Z. Transports badge', circular example bearing central Crown within the title surround, the reverse with maker's details 'C.M.Bay, Wellington, New Zealand'. Very good condition, retaining original buttonhole fitting left side point slightly gnarled. Diameter 26mm. Non-combatants who volunteered to drive ambulances during the First World War were designated 'His Majesty's New Zealand Transports' (HMNZT).