Great British Line Engraved Stamps Issued 1840-1879
The first stamps issued used a printing process known as Line Engraved. Plates were engraved by highly skilled engravers. Ink was applied to the plate and the excess wiped off. Paper was then pressed onto the plate, forcing the paper into the recessed areas, thus leaving the inked part of the plate transferred to the stamp. When you consider that 240 stamps were printed from each plate and it is almost impossible, if not impossible to tell what plate the stamp came from by purely looking at the engraving. There are ways to tell for most stamps, but this is a very skilled part of collecting and has been made easier for collectors of today, only by people who spent years and years researching. Most of us use these reference works.

If you look at my Line Engraved section of the site, you will see that the first plate used for the Penny stamp was obviously plate 1 (actually 1a and 1b) and the last was plate 225. Plates were replaced as they wore out. A few were not used at all, mainly as they failed quality control. Line engraved issues are all many collectors collect. This is because the area of what can be collected is vast. Just to give you a brief idea:
First you have the Penny Black, plates 1a through to 11 (11 being very scarce as it only had a short life).

• 2d Blue, plates 1 to 15.
• Penny Reds plates 1b through to 225.
• ½d Reds – Plates 1 to 20
• 1½d Reds – Plates 1 and 3.

All with 240 stamps to a sheet (½d had 480, as they were only half the size), each stamp with different check letters at least in the bottom two corners (this, along with the watermark were security measures against fakes. Top left was AA working across the AL, then down to the T row). So, to have a truly complete collection of line engraved GB stamps, you would be talking about 60,000+ stamps!
Then you have the postmarks. Red Maltese Cross at first, then Black, then Town cancels etc. Postmarks as we call them today were not called that at first. They were actually obliterators and were meant to do just that, obliterate the stamp to stop it being used again. Many collectors specialize in collecting postmarks from this period.
At first the sheets of stamps were imperf, with no perforations and all the stamps had to be cut out using scissors. Postal workers were meant to take care when cutting them out and insure that they cut in the margins surrounding each stamp. In practice though, this was not done very often, hence 4 clear margin stamps commanding a price premium. The Penny Black was soon replaced by the Penny Red as it was decided that Black was not really a suitable colour and that it was not difficult to find stamps that could be used again as the postmark failed to show up clearly enough. Perforations were developed to aid in the tearing of the sheet. Roulettes were tested at first and early trials using both these methods are scarce if not rare and again command a premium. At first there were no plate markings on any stamps and collectors have to use certain characteristics found only on a particular stamp to aid plating. In 1858 the plate numbers were for the first time incorporated into the design of the 2d Blue values. It wasn’t for another 6 years, in 1864 that visible plate numbers were used for the Penny red. An example of what to look for is shown below.

With the Introduction of this issue, SG 43/44, came the first Visible Plate Numbers. All Previous Issues can only have the Plate Number determined by Certain Characteristic Markings etc. In this Issue, the Plate Numbers can generally be clearly seen either with the Naked Eye or a Reasonable Magnifier. In this example you can see the numbers 189. The numbers can be seen vertically on Both the Left and Right hand sides of the stamp.