Constant Plate Varieties 101:
Plate Varieties Related to Siderography and the Transfer Roll
Although constant plate varieties can originate at several stages in the printing process, many of the most interesting and collectable are created during siderography when the transfer roll is used to transfer the impression for each stamp position onto the printing plate. Below are some basic definitions and descriptions of varieties related to siderography and the transfer roll.
Re-entry:
A "re-entry" is a constant plate variety caused when the transfer roll is used more than once to transfer the design to the same position on the plate, causing a doubling or even tripling of the stamp impression to be visible on the final printed stamps. Re-entries can occur when a plate is initially created or during later repairs to the plate after it has been used for printing. There are several types of re-entries and the terms to describe them are not always used consistently in the philatelic literature.
The most common type of re-entry occurs when the transfer roll is deliberately reapplied to strengthen a poor impression caused by plate wear or insufficient initial transfer when the plates were originally created. The re-entered impression is laid down over the existing impression but is unintentionally slightly out of alignment causing the remainder of the original impression to appear as doubling in the printed stamp. If this was done during the initial creation of the plate, the re-entry will appear on the plate proofs and for the entire print run unless it is later corrected. The term "initial re-entry" is often used to describe these re-entries that are created on the initial plate before it is actually used for printing.
Fresh Entry:
Another term that is sometimes used to describe any re-entries that appear on the initial plate is the "fresh entry". This term is derived from the fact that impressions on the initial plate that are unsatisfactory, are often burnished out and a new "fresh" impression is made in their place before the plate is put into use. If the burnishing of the initial impression is not complete, traces of the original entry may show up to reveal doubling in the printed stamp. The need to remove the initial entry instead of simply reapplying the second entry straight over it is usually caused by more severe problems or a significant misalignment of the initial entry. When fresh entries show up in the final stamps they are usually isolated to particular sections of the impression that were not burnished out correctly and may show significantly wider displacement between the separate entries than a traditional re-entry would. Since the burnishing out of an impression and entry of a new fresh impression can also be done during later repairs to a plate, Ralph E. Trimble at re-entries.com argues that this term should be used for all new entries made after burnishing the plate and not just those performed during the initial production of the plate. I agree with that assessment and will try to use this terminology throughout the commentary on this site.
Misplaced Entry:
A final type of severe re-entry is the "misplaced entry". This is caused when the transfer roll is misaligned to the point where it begins to rock an impression on the plate that is significantly out of alignment with the other stamp impressions. This is usually discovered quite early in the rocking process so that the transfer roll can be lifted and moved to the correct position to complete the entry of the impression in the correct position. It must be assumed that many of these partially rocked-in misplaced entries would be burnished out before re-entering and that others would have all or most traces obliterated by the second entry. The small number that exist on Canadian stamps usually only exhibit traces of the original misplaced entry in a very specific small horizontal area of the final stamp, although they can still be quite dramatic.
Foreign Entry:
Very occasionally, an impression from an entirely different stamp on the same transfer roll or from using the wrong transfer roll is accidentally partially transferred to a plate. This is called a "foreign entry". It may also occur when the transfer roll is over-rocked such that, in addition to creating the desired transfer on the plate, a partial transfer from a second impression on the transfer roll is also rocked into the plate well above or below. This partial transfer would then appear in the stamp positions immediately above or below the over-rocked impression.
Of course, a transfer roll that only has multiple impressions of the same stamp and denomination can also be over-rocked so that it produces partial transfers above or below the desired transfer. This is not usually referred to as a "foreign entry". I would argue that it is a form of "misplaced entry".
Short Entry / Short Transfer:
As its name implies, a "short entry" or "short transfer" occurs when an incomplete impression is transferred from the transfer roll to the plate. This can be caused by insufficient or incomplete rocking of the transfer roll, or to anomalies in the plate surface and pressure applied during the rocking-in process. The appearance of the incomplete impression on the final printed stamp is similar to the appearance of stamps with plate wear, except that short entries/transfers will show a deep, sharp impression for most of the stamp and only a single area of the stamp (usually at the top or bottom) will exhibit the much lighter or even missing impression. Short entries/transfers can occur when the original plate is created and may often be visible on plate proofs.
Relief Breaks and Other Transfer Roll Damage:
Scratches, cracks, and other marks from damage to an impression on the transfer roll can result in varieties that exit for significant parts of a single plate or throughout many different plates created using the damaged transfer roll.
If there is only one impression on the transfer roll and it is damaged in some way and then used for all plates of the entire print run, then the damage will show on all stamps of the issue and cannot be considered as a variety. The best example of this is the prominent relief break from cracks or scratches that appear on Canada's first postage stamp. All of these stamps were produced from the same impression on the transfer roll and they all exhibit some evidence of a thin jagged line that starts near the beaver's front paw and proceeds upwards through the beaver's body and into the oval portrait frames where it splits and flows out through the top and right sides of the impression.
While Canada's first beaver stamp is an extreme example of an initial and constant relief break, there are many others more minor types of damage that can occur to the impressions on the transfer roll that only appear on certain plates or specific positions on any given plate. If damage to the transfer impression occurs during the plate-making process, it may only appear on specific plate positions as they are rocked in. If the damage is noticed, a different impression from the same transfer roll can also be used on the same plate. Like plates, transfer roll impressions are also subject to wear and they can change over time and repeated usage.
It should also be noted that intermittent damage can also occur to the transfer roll impressions such as stray bits of metal or other hard matter that could adhere to the transfer roll or potentially block some of the relief lines as they are transferred to the plate. Sometimes, this type of damage can be cleaned away or even worn away as the transfer roll is used.
The key point about varieties created by damage to transfer roll impressions is that they will almost certainly appear on more than one position on the plate. Even changing to a different impression made from the same die may sometimes show minute differences on the plate that show up as varieties on the printed stamps.