Type 47

This overprint is believed to be for the Parliamentary Papers Sales Office.  According to a Post Office Commercial Directory of 1865 they had outlets at:

    House of Lords,
    Old Palace Yard,
    Westminster,
    London S.W.

    13 Great Queen Street,
    Lincoln’s Inn Fields,
    London W.C.

and

    32 Abingdon Street,
    Westminster
    London S.W.

Their opening hours are stated as being “10 to 4”.

1874. Unofficial overprint type 47 in purple, reading upwards.

PP166 1d lake-red (SG 43 or G1)
Plate 176