Just east of the main entrance to the main Royal Mail Sorting Office is a small and inelegantly landscaped niche. Just to the left of the war memorial in the niche is a Liverpool Special Pillar Box. These were cast from 1863 onwards by Cochrane, Grove & Company of Dudley and were unique to Liverpool. Richard Redgrave had designed a pillar box for use in London & other large cities in 1856. This design was amended with practical improvements at least twice but it was not suitable for locations which received a large volume of mail. The Liverpool Special was significantly larger. This example was sited here in 1978 having formerly been in use in Everton and is one of only three surviving examples, one of those being in the Post Office Museum.

Source: http://postalheritage.org.uk/history/