1935 Silver Jubilee 2½d. Prussian blue, S.G.NCom14,

marginal block of 4 from the right of the sheet with marginal guide and punched hole, superb colour, a few split perforations, large part original gum, the lower left stamp unmounted. B.P.A. Certificate 1999. AN EXTREMELY RARE BLOCK OF THIS FAMOUS ERROR OF COLOUR.

The correct issue colour of the 2½d. is blue and for many years it was thought that the stamps printed in Prussian blue came from sheets of Colour Trials which had been issued in error.

Colour Trials were however printed in a larger format than the issued stamps. The Prussian blue stamps are in the issued stamp format so cannot be classified as Colour Trials but an issued 'error of colour'. Four sheets in this colour were released from the Post Office Stores Department on June 25, 1935. These sheets were sold from a Post Office in Edmonton, North London between that date and July 4 of the same year.