UK Sg X842 (Full Perfs) And Sg X482 (Trimmed)

Classifying my UK stamps I found these references SG X842 (Full perfs) and SG X482 (Trimmed) ,"½p Turquoise Blue (Left Band)",
Among my stamps I found this, but I don't know if it refers to the bars that can be seen in the photo, the first with 3 bars, the second with a bar on the left and the third with a bar on the right… I thought you US stamps were complex, but the UK ones are really explode my head...

These bands are called phosphor bands. On older stamps (1950-1993), use a short-wave uv light, on never issues (after 1993), use a long-wave uv light to make them glow.
Just google "Machins Phosphor bands" and you get drowned in information.

You can use shortwave on all of them. From ca. 1992, longwave, also, can be used, but not always.
The left one has two bars. I do not know where you see a third bar. The right one has two side bars as well. This stamp does not exist with a right bar and the bar at right is not wide enough to be a shifted 9.5 mm bar at right.

The stamp with the bar at left is half a 9.5mm bar applied over two adjoining stamps of which the 1/2 p stamps was the right one, thus having a ca. 4.75 mm bar at left. This came from a Prestige Booklet. These were cut in such a way that the majority of stamps had the perforations at right trimmed, sometimes also the perforations at thebottom of the stamp.

Full SG catalogue price is for a stamp with full perforations on all sides. The ones with trimmed perforations at right, bottom, or right and bottom are worth considerably less.

I have serious doubts the middle stamp is a left-bar stamp. The perforations at the bottom are irregular. This does not fit a stamp cut right and bottom. All these stamps with the left bar are cut at right and bottom. It looks like that is a two-barred stamp as well. I cannot say for sure, but I think you might want to have a closer look at the middle stamp.

Thank you!! With the UV light everything has been revealed, and I can see the lines perfectly, even those invisible in normal light... I found this specimen (in the center of the photo) What do you think, could it be an SG x482?

Two bars, ????, and centre bar. No left bar.
That centre stamp still gives some cause for doubt. It may be the PCP sheet stamp issued in 1980.

Are the stamps wet or dry? There appears a lot of contamination of the centre stamp.

They are dry. The contamination is some scratches that unfortunately the stamp has...

99% sure that centre stamp is a PCP stamp, i.e., it has no phosphor bar, but a coating with the phosphor mixed into it.

You kill me....An open door to more variants?

You can collect Machins at several levels of specialisation. If you collect them used, at least you do not have to worry about the different types of gum. The 1/2 p is a very simple one. It comes with 2 (half) 9 1/2 mm bars, two 8 mm bars, a centre bar, a left bar, and phosphor-coated paper. The phosphor used is Lettalite B3 that fluoresces violetish.

The 1p, 2p, 5p, 10p, 20p come in multiples of that number of varieties. Think 30+ varieties at even a basic level. Ignoring accidental varieties, were quite far on the way to 100 varieties.

I would say 'Knock yourself out with this one:'
http://connoisseurcatalogue.net/catalogue.htm

Note, you will find the 1/2p in chapter 2, sections a (2 varieties), b (2 varieties), c (3 varieties), d (9 varieties), f (13 varieties), j (1 variety), and k (1 variety). The other values I mentioned are spread over several chapters.




I hope you paid your life insurance premium.

really grateful!!! With this, I have a lot of work, desperation and fun waiting for me...

It's really crazy...it will be a long time before I manage to put my entire collection correctly in order, if I ever do.. Does missing match mean that it doesn't have bars? please, is the central stamp an example of missing phosphor?

Actually, it looks like the all-over phosphor stamp.

What is missing phosphor? Is it a stamp that does not shine nothing (like 1958) or a stamp without bars?

Since the 1960s, British stamps had phosphor bars applied. The afterglow could be recognised by optical scanners that would then know where the stamp was. Also, it could count the number of light signals per time unit. That allowed the scanner to identify items of mail that had a stamp with a single bar (paying second class carriage) from other stamps.
Locating the stamp allowed for the automatic letter sorting machine to turn the cover so the stamp would appear in one of two quarters (no one considered the clown sticking it in the centre of the cover) before passing it through the canceller.
Counting the signals allowed the automatic letter sorter to sort out second class mail from other mail (originally it was printed matter from letters).

Two phosphor applications exist:
1. Printing phosphor ink. The bars were applied by a printing cylinder as phosphor ink that contained a phosphor and an activator. A couple of stamps, basically, had one stamp-wide bar applied (all-over phosphor). But in most cases 8, 9, or 9.5 mm (in the 2000s other formats occurred with self-adhesives) wide bars were applied over two adjoining stamps, or 4, 4.5, or 4.75 mm wide bars were applied over the centre of a stamp.
2. Phosphor was mixed into the paper coating: phosphor-coated paper or advanced-coated paper. (By that time, the scanners could distinguish between a single bar and a coated stamp).




Strictly speaking, missing phosphor means the stamp has no phosphor applied. However, it is used to indicated that the phosphor ink was not printed onto the stamp. So, yes, without bars. In the case of an all-over phosphor stamp (but no way to differentiate from its double-barred sibbling) the all-over phosphor was not printed.

For stamps that should be printed on phosphor-coated or advanced-coated paper, it should be easy to realise that a missing phosphor implies the phosphor was not mixed into the coating (I am not aware this happened), or the coating is missing. The latter makes it an 'uncoated' stamp.

So, effectively, missing phosphor = no phosphor bars were printed onto the stamp.

From 1972 until the 1990s, the coating had an optical brightener mixed in. If the phosphor is missing, the stamp might still show 'fluorescence' and 'shine.'

Phosphor emits an afterglow, that is not the bright 'shine' you see under longwave uv light.

If you want to know how this all worked and collect these 'Machin' stamps I can recommend buying the Deegam Handbook. It has appendices that explain how the stamps were produced.

I'll try to get it!!!
I must rethink my entire classification strategy... it is very very very complex... in the first phase I will not classify paper or gum...
1 I will separate by values
2 I will separate by bars,
3separate head type and figure
I will separate those that come out of the 2 bars or the central bar separately to review them calmly and have them located.