This is a superb example of the Wrenn W4657 "United Dairies" 6 Wheeled Milk Wagon in white with Yellow UD Letters. Introduced by Wrenn, Basildon in Period 2 (Triang/Wrenn) this just survived in production until early Period 4. This is one of the Period 4 (Type W7304 Box) examples and is becoming difficult to find today in this packaged form. As with all P4  wagons it has pin wheel axles and metal rimmed wheels.

Complete with P4 box and yellow plastic insert.

Wagon/box are "near mint" considering age.