"Four plate numbers, each consisting of a ring surrounding a circular plug in which the numeral ‘1’ has been left colorless, were incorporated into the key plate to the left of cliche's 1 and 49, and to the right of cliche's 12 and 60. In printed sheets, the plate numbers are in the same color as the printed portion of the key plate.
Contrary to the duty-plate cliche's and jubilee line, the key-plate cliche's often suffered damage before or during printing. When repairs were made to the cliche's before each printing, the four plate numbers were also checked for damage. And as with the key-plate cliche's, plate-number repairs did not last. Over the life of the King George V issue, both the outer ring and the center plug, especially those at positions 12 and 60, underwent extensive damage.
Some collectors have suggested that the appearance of a plate number could be used to identify the printing of the stamp to which it is attached, but this is not, in fact, a reliable indicator. Damage to plate- number repairs often occurred as printing was in progress, but not all repairs broke down during all printings. Thus if a repair held up during a particular printing, the plate number at the end of the printing looked the same as at the beginning; if the repair broke down, however, the appearance of the plate number at the end of the printing differed from that at the beginning. The state of repair of a plate number is therefore not a definitive characteristic of a specific printing.
If a plate number from a particular printing shows less wear than that from an earlier printing, then it is obvious that a repair was made at some point before the later printing." [M.Glazer]
Two shillings six pences SG 89 plate number block of four.
Plate number is not damaged yet.
Bermuda two shillings six pences SG 89g block of four stamps
from lower-left corner of sheet with plate no. 1. This unmounted mint
block with one stamp showing Plate Flaw 50 (bullet hole state II)
was sold at Grosvenor Auction in 2007 for ?300 plus buyer's premium
Plate number is damaged.
Bermuda two shillings six pences SG 89jg, from lower-right corner of sheet
with plate number (and Plate flaw 60E). This mint vertical pair (one unmounted)
was sold at Grosvenor Auction in 2007 for ?320 plus buyer's premium
"On a printed sheet of stamps, the “jubilee line” is a broken line, in the same color as the frame, that surrounds the block of stamps (i.e., the 60 stamps, in the case of Bermuda’s high-value stamps). The addition of this line on the printing plate, as described in Williams’ Fundamentals of Philately, was meant “to protect the edge of the subject on the printing base from damage by the inking roller.” As the aim of the printers was to produce a uniform impression and thus obtain a high-quality printed image, it was important that the cliche's on the periphery of the plate be protected from the force of the impact of the impression cylinder hitting the duty plate, so that repairs done to the cliche's would not break down as quickly and there would be less opportunity for flaws to develop. Because the jubilee line was meant to absorb that impact, it was raised very slightly above the surface of the plate and was printed at the same time as the cliche's.
Although the King Edward VII key plate had a jubilee line, the King George V plates first made in 1912, and two more made in 1926 did not, for reasons unknown. However, each of the eight duty plates prepared for Bermuda’s King George V issue contained a jubilee line. This consisted of a thin piece of copper (about one eighth of an inch thick) produced in the same manner as the plate itself, and held in place by two screwed-in flanges - one at the top between cliche's 6 and 7, and the other at the bottom between cliche's 54 and 55. As the jubilee line surrounded the plate, it was situated above cliche's 1 to 12; to the right of cliche's 12, 24, 36, 48, and 60; below cliche's 49 to 60; and to the left of cliche's 1, 13, 25, 37, and 49. The line was not continuous but was broken between each cliche' to allow air trapped between the plate and the paper to escape during printing, thus preventing the paper from moving or creasing and the stamp image from becoming distorted. There were additional breaks in the middle of the jubilee line above cliche's 6 and 7 and below cliche's 54 and 55, where the flanges held the line. Also in the margin surrounding the stamps were registration lines, used to identify the position of the stamp in a sheet of 60. These lines were placed above cliche's 6 and 7, and below cliche's 54 and 55.
The jubilee lines of the eight duty plates do not appear to have suffered any damage during printing: on all stamps with selvedge seen by the author, the jubilee line has a uniform appearance and is in the same color as the frame ink. The only exception is a break in the jubilee line above stamp no. 2 of the June 1921 printing of the 5s value." [M.Glazer]
Bermuda two shillings six pences SG 52 block of 4 with additional break in
the middle of the jubilee line below position 54 and with registration line.
- The King George V High-Value Stamps of Bermuda, 1917-1938, Myles Glazer, 1994