B = Business box

The official Royal Mail name for large sheet steel and aluminium boxes erected in large numbers on industrial estates and in business parks and districts to receive sealed postal pouches of Meter Mail. The boxes first appeared in 1994. There are a number of minor variants in design. The boxes are manufactured by Romec, the part-owned company that emerged from Royal Mail’s engineering division.
The Letter Box Study Group
2016-02-10T16:15:06+00:00
The official Royal Mail name for large sheet steel and aluminium boxes erected in large numbers on industrial estates and in business parks and districts to receive sealed postal pouches of Meter Mail. The boxes first appeared in 1994. There are a number of minor variants in design. The boxes are manufactured by Romec, the part-owned company that emerged from Royal Mail’s engineering division.