This exhibit by Hugh Armstrong explains the use of a ‘diamond mark’ which was used by the Royal Mail of Great Britain to study and count the volume of mail being processed. It was in use from about 1923 until 1985 and it indicates that the item had, in fact, been counted.
















Postal Census Slogan Cancels
Postal census slogan cancels have been found between 1937 to 1951 but probably continued to at least 1966.