Type 10

Cocker Brothers Limited were Spring Manufacturers in Sheffield.

1874. Unofficial underprint type 10 (over the gum) in black.

PP21 1d lake-red (SG 43 or G1)
Plates 174, 191, 195, 196, 198, 199, 208, 212, 215 and 218

PP21a 2 1/2d blue (SG142  or J21)
Plate 19

There are a number of later perfins that have also been (provisionally) identified as belonging to this firm.    I do not have illustrations of these perfins but they are referenced in Tomkins as:

See the Philatelic Links and References page for more information on Perfins.