[1] Designed by Arnold Machin, the stamps consist simply of the sculpted profile of the Queen and a denomination, and are almost always in a single colour.
Arnold Machin's 1964 effigy of Elizabeth II was replaced on British coins in 1984 by an older-looking portrayal by Raphael Maklouf.
[6] The project waited until the miniaturisation of the new definitive effigy that the Stamp Advisory Committee (SAC), on 13 January 1965, had advised the Postmaster General be chosen, from profiles and engraved images based on a photograph.
The competition began with more artists officially invited during Summer 1965,[9] but at a meeting on 26 January 1966, the SAC's members decided to let only Gentleman and Machin continue work on the design.
[10][11] Machin's method was to sculpt a bas-relief in clay and moulds, which he reworked and corrected depending on what the SAC required.
Quickly, he decided to simplify the effigy with just the Queen wearing the Diamond Diadem and its bouquets of national flower emblems, like the Wilding series.
Elizabeth II selected the pictures to be given to the artists and Gentleman continued work on the "photographic alternative" to Machin's sculpture.
[18] But the Post Office did not fully respect Machin's views and in the first years of the series would also issue bi-coloured stamps and clear-to-dark graduated backgrounds.
From the philatelic point of view, the "Machins" are far more complex than the simple design might at first suggest, with well over five thousand varieties of colour, value, gum, phosphor banding, iridescent overprints, perforations, printing methods (Photogravure, Intaglio (Engraved), Typography, Electro-Mechanical Engraving (EME Gravure), Embossing) etc., known.
Initially the stamps were produced by Harrison & Sons using photogravure, with the high-value designs being larger and engraved (intaglio) by Bradbury Wilkinson and Company.
The following year of 1990 brought forth the first commemorative adaptation of the Machin design, with the classic William Wyon profile of Queen Victoria, Queen Elizabeth II's Great-Great Grandmother, appearing behind and to the left of Elizabeth, marking 150 years of British stamps, namely the Penny Black 1d stamp of 1840.
1993 saw the introduction of both self-adhesive stamps and elliptical perforations on the lower vertical sides of the Machins, the latter as a security measure.
[21] On the high value stamps, an iridescent ink by the brand name of "Iriodin"[22] was used to give them a shiny, pearlescent appearance and ensure the difficulty of their reproduction by photocopying.
These two later features were intended to render the stamps difficult to take off mail and to store for reuse (but in effect are easily overcome by the careful use of a sharp knife edge).
[25] The security features also included a minute change to the background printing of "ROYAL MAIL" where one letter is replaced to identify the source of the stamp.
The dark olive-brown shade of the 4d value, the most often-used stamp of the time, was personally selected by the Queen as being the available colour most reminiscent of the Penny Black.
However, in practice this proved difficult to distinguish from the 5d's dark blue, automated machinery could not always see the phosphor bands on the stamps, and even football pool organizers complained that it was too hard to read the date and time of cancellations.
On three occasions, postal sources have confirmed that a replacement for the Machin series was proposed by the Post Office, and its successor, the Royal Mail.
[26] The Post Office's Ron Dearing obtained agreement from the Queen, even if she expressed through a letter by her deputy private secretary that "Her Majesty is very content with the Machin effigy and thinks that a work of real quality is required if this is to be replaced.
"[27] Under the supervision of Post Office design adviser Barry Robinson, Jeffery Matthews prepared alternative essays from March 1982 pictures of the Queen by Lord Snowdon.
[28] In 1983, Robinson ordered new portraits by different artists: drawn by John Sargeant, painted by Timothy Whidborne and Brian Sanders, later engraved by Czesław Słania in 1984.
It comprised a bicoloured (grey effigy on a coloured background); Jeffery Matthews then worked on a different cut of the shoulders and neck, for a horizontal stamp.
[30] As Arnold Machin had to be informed on any modifications of his original design, Barry Robinson and Jeffery Matthews visited him on 23 October 1985.
The fact that printers and printing methods change so frequently means that collecting Machin stamps remains popular.
[citation needed] As is usual with a new printer, such as happened when Enschede, Waddington, Questa and Walsall were engaged, subtle changes occur, giving rise to new varieties.
A five-pane prestige book was issued for the 50th Anniversary of the Machin series with one of the five panes printed in 22kt gold foil and embossed as a block of four.
The first British stamps of the Machin series served as such in the Crown dependencies before their postal independence: Guernsey and Jersey until 1969 and the Isle of Man until 1973.
[34] In April 1996, the United Kingdom one penny Machin stamp was overprinted and used for a few days in Somaliland,[35] a state that self-declared its independence from Somalia in 1991.
Due to an insufficient stock of paper, the British printer Harrison and Sons could not deliver in time a stamp issue ordered for Somaliland.
Canada Post issued a domestic rate stamp on 7 February 2022 using the Machin design, to mark the Platinum Jubilee of Elizabeth II.