This is an excellent example of the RARE Wrenn W.5086 6 Wheeled Tanker Wagon, packaged in the standard short Box version. The Tanker is white, running number 172. Introduced by Basildon through Period 4, this continued with limited production until closure in 1992. As with all Period 4 Wagons it has metal rimmed wheels. Many examples of this wagon had "browning" of the white plastic this HAS NOT. 

This Tanker Wagon comes in a Period 4 (type W7304)  with split yellow plastic insert .

Condition of the Tanker/Box is "near mint  " for their age.