"head-to-head") is a joined pair of stamps in which one is upside-down in relation to the other,[1] produced intentionally or accidentally.
Mechanical errors during the process of production can result in tête-bêches.
Where the columns of stamps from each side meet there is therefore a row of tete-beche pars.
A block of 24 5d Machin stamps, which should have been guillotined into four booklet pages, includes four tête-bêche pairs.
This was sold in 1970, in the normal course of business, by the British Post Office and is exhibited by a member of the Royal Mail Stamp Advisory Committee.