In response to several posts about plate varieties and inking differences, I thought it may be helpful to provide a very basic
overview of plate varieties in early U.S. engraved stamps.
There are 3 basic step to making a plate
1. Produce master die
2. Produce transfer roll
3. Lay down plate
The master die is cut in a mirror image of the stamp and hardened. The areas that are relieved (cut away) are the areas of the stamp that will receive the ink. Any error made on the master die will appear on all positions of the plates associated with that die. An 1851 3˘ essay master die and die proof are shown below (this Rawdon, Wright, Hatch and Edson design was not approved).
The circled area shows an engraver's slip and the resultant effect on the outer frameline.
The design of the die is reproduced onto the transfer roll. This transfer is done by traversing the die back and forth while pressing it into the roll as shown in the line drawing below. Each reproduction of the die onto the transfer roll is called a relief. The transfer roll will have several reliefs. Any errors or differences in the reliefs will be transferred to all plate positions made from that relief. After the reliefs have been transferred, the roll is polished and hardened.
A transfer roll showing 2 reliefs is shown below.
Transferring the master die design to transfer roll
Above are 3 of the 6 reliefs produced by the transfer roll (#4) used for the 1857 perf 15˝ 1˘ stamp on plates 5*, 7, 8, 9 and 10. Although they were made from the same die, each of these reliefs are slightly different. They are all Type V and produced the Scott 24.
*Some positions in Plate 5 were Type Va from roll #3.
Plate lay down
The plate subjects are entered in a process that is similar to that used to make the transfer roll except that the design on the roll is pressed into the plate. The plate is rocked (moved back and forth) transferring the design.
Lay down of a plate
This process is the cause of 3 types of errors/varieties:
Short or weak transfers
Short transfers and weak transfers are caused by not rocking the plate far enough to achieve a complete design transfer into the plate. A short transfer would have portions of the design missing while a weak transfer would show the features broken (such as a frameline having dashes instead of solid).
Scott 2 short transfer at top note the absence of the shading lines at the top and the incomplete ornaments above the "ST" in "POST".
Double (Triple) transfer is a second (third) misaligned transfer of lines from the transfer roll relief. This is caused by either replacing an erased entry where the previous entry was not totally removed by burnishing or by re-entry to strengthen an existing entry.
Scott 7 Position 89R2 double transfer at bottom left. Arrow indicate some of the more prominent doubled lines.
Damaged transfers are normally caused by either foreign materials between the roll and plate during transfer or by relief break where a part of the transfer roll relief breaks off.
During the transfer a small curl or thread of the metal from the plate may break loose. The pressure of the transfer process will press it into the plate. When the plate is used that position will show an ink mark at the location of the damage.
During the transfer a small piece of the metal from the roll may break off. With part of the relief missing the design will not be pressed into the plate. When the plates are used all positions entered from that relief will have the damaged area unprinted.
Scott 6 Position 97L4 Curl on Shoulder caused by a metal thread only on this position.
Scott 7 Position 7L3 Curl in "S" caused by a metal thread only on this position.
Scott 6 Position 97R4 Curl in "C" of "Cent" caused by a thread adhering to the relief on the transfer roll. The thread attached itself to the relief on the transfer roll after Position 57R4 was entered. The variety is then found on Position 97R4 and also on Positions 56R4, 96R4, 55R4 and 95R4. The thread either dropped off or was removed after entry of 95R4, as 54R4, the next position to be entered from this relief, does not show the variety.
Scott 231 Broken Frameline at Bottom Right caused by relief break on transfer roll.
1 shows complete frameline, 2 shows two short breaks, 3 shows a small section connecting three shade line left, 4 shows a small section connecting two shade line left, 5 shows final breakage.
Additionally, any mis-handling of the plates can cause a ink indication. Any scratch or indentation will hold the ink and transfer it to the printed sheet.