The 4d olive sepia Machin with Head B and Gum Arabic

It wasn't long after the Machins appeared on June 5, 1967 that they started the unceasing evolution that endears them to us.

One of the first two significant changes was on the back of the stamp, and the other was on the front.

The first Machins appeared with gum arabic, a natural product from acacia trees in Sudan. Paper with this gum tends to curl, so the gummed paper was passed over a fracture bar to break up the gum. As a result, it has a glossy, sparkly appearance. It is generally abbreviated GA.

Because of concerns about reliable supply, in January, 1968, Harrisons and Sons started using a synthetic gum, polyvinyl alcohol. It is less shiny, or matt. It is usually abbreviated PVA, but Douglas Myall uses the official abbreviation, PVAl, to avoid confusion with polyvinyl acetate (PVAc), which has been used on some airletter flaps.

The change to PVA was permanent, but gum arabic was used for Machins again briefly in 1972/73.

There is, of course, a long story about the colors and appearance of the various gums over the years, but I'll leave that for another time. Roy's page on Machin gums is here.

The second change involved the portrait. Most of the original Machins had a version that became known as Head A. In February, 1968 Harrisons began using a second image that was derived from a different photograph of Machin's plaster cast. This version, known as Head B, had a more three-dimensional, lifelike appearance than Head A.

Head A is on the left in the images above, Head B on the right.

Head B replaced Head A and remained in use after the conversion to decimal currency. Head B was also the basis of the digital image that was introduced in 1997.

There are a number of differences between Head A and Head B. The one most commonly used by collectors to differentiate the two is the base of the portrait. On Head A, the base is flat, and the fold that starts at the back of the Queen's neck at the top of the corsage (dress) extends to the bottom of the portrait. On Head B, the base is rounded, and there is a visible amount (about 0.5mm) of corsage below the end of the fold.

There are variations of Head A and Head B, as well as several other heads. Again, that is beyond the scope of this post. Roy's page on Heads A and B is here, and Robin Harris' page is here.

Okay, back to the 4d. When it was issued, it paid the basic inland letter rate, so a large quantity of the stamps was used. This denomination was converted to PVA gum in January, 1968, and to Head B in April, 1968. So, the first stamps were Head A with gum arabic, then came Head A with PVA, and then Head B with PVA. In theory, there should not be any Head B with GA.

However, in the summer of 1968, Harrisons apparently used up a roll of GA paper to print the Head B version of the 4d. It was printed from cylinder 14, which was then in use, so it is clear that the stamps resulted from the use of the wrong paper.

Douglas Myall notes that fewer than 100 copies are known today. The only six known cylinder blocks are all no dot and were all purchased on the same day at the same post office. If indeed a whole roll of paper was used, there may be more copies lurking out there, though no doubt most were used for postage.

Today this stamp sells for well over £1,000, when you can find one. Although it resulted from the printer's misstep, catalogs treat it as a regularly issued stamp, thus the unfilled space in my album.

--Larry

Much of the information herein came from Douglas Myall's Complete Deegam Machin Handbook. If you have a copy, Myall has a brief note about this stamp in item 51 of the file guidec95.pdf in the archive folder. My thanks to Douglas for reminding me of this.