By Michael Baadke
Our past three Refresher Course columns have followed the evolution of United States plate blocks from the earliest examples of classic stamp issues printed by flat plates to the oversized blocks that appeared on rotary-press issues during the late 1960s and the 1970s.
As printing methods and machinery have changed, so has the appearance of the plate block.
The earliest plate blocks consisted of two rows of stamps from one edge of the stamp pane, with marginal inscriptions and the printing plate number centered on attached selvage. These plate blocks often consisted of six, eight or more stamps.
As the rotary press was used with increasing frequency during the 1920s, the most common plate block was a corner block of four stamps with all attached margin paper, including plate numbers.
This format remained fairly consistent for 40 years, and it continues to be the established plate block layout for many of today's issues.
The Scott Specialized Catalogue of United States Stamps and Covers helps the collector understand plate block configurations with descriptive listing information.
In the 1990s two new developments particularly affected collectors of plate blocks: the pane position diagram and the change to four plate blocks on each pane.
On July 24, 1992, the Postal Service issued a pane of 50 29¢ American Wildflowers stamps. The stamps were manufactured by Ashton-Potter America Inc. on two different offset presses: one produced sheets containing six panes (or 300 stamps total), and the other produced four-pane sheets of 200 stamps each.
Both sheet sizes were trimmed into panes of 50 that were sold at post offices.
For the interest of collectors, though, each pane of 50 stamps included a diagram that showed which size press sheet the individual pane came from.
The Figure 1 illustration shows the diagram that appears near the upper-left corner of a pane from the four-pane sheet.
The upper-left box of the four boxes in the diagram is shaded to indicate that the pane this particular diagram appeared on came from the upper-left section of the full press sheet.
Similar diagrams continue to appear in a modified state on many of today's stamp issues.
The diagram is labeled "PLATE POSITION" on recent issues, but it is referred to as a pane position diagram by Linn's Stamp News, for it shows the position of the pane in relation to the full press sheet.
Figure 2 shows an uncut press sheet of the 32¢ Stephen Vincent Benet stamp issued July 22, 1998.
While many recent stamps have been sold to the public in press-sheet form, the Benet stamp was not. The photograph of the sheet shown here was provided by the U.S. Postal Service.
As you can see, the Benet press sheet consists of nine panes of 20 stamps.
Enlarged at top right in Figure 2 is one of the nine pane position diagrams that appear on the sheet. One diagram is found directly below each of the nine blocks of 20 stamps on the sheet.
For some issues the diagram can be collected as part of the plate block. This is true for the Benet stamp, as the diagram appears on each of the lower-left plate blocks from each pane.
Figure 3 shows a collection of nine plate blocks that represent the nine pane positions of the Benet press sheet. The diagram on each block indicates a different location on the press sheet.
This type of collection is similar to the collections of matched plate blocks that were formed by enthusiastic collectors earlier this century.
The diagram is not an essential element of the plate block, however. Although the Scott U.S. specialized catalog notes for some issues that "Some plate blocks contain plate position diagram," collectors interested in saving just one plate block for each issue are not required to seek out a block that includes the diagram.
On the other hand, in recent years the diagram has become the only indicator of the pane position that collectors can rely upon. As early as 1992, the Postal Service began issuing first-class-rate stamps in panes of 20 with plate numbers appearing in all four corners of every pane from the press sheet.
The single plate number on most rotary press issues had previously been a reliable indicator of the pane position. If a corner block of four stamps had margin selvage and a plate number adjacent to the upper-left stamp in the block, this showed that the plate block had come from a pane from the upper-left position of the press sheet.
With numbers at all four corners of every pane, that indicator was suddenly no longer valid.
The introduction of the pane position diagram became a necessity for specialists who desired pane location information.
Figure 4 shows a pane of 20 32¢ Lila and DeWitt Wallace stamps, Scott 2936, issued July 16, 1998, as part of the Great Americans series.
The plate number "P1" is visible in each corner of the pane. The plate block for this issue contains four stamps.
Collectors may choose to save any or all of the four plate blocks that appear on this pane. To include the pane position diagram, some may decide to save a block of six or 10 stamps from the bottom half of the pane.
Such decisions are completely up to the collector.
While the new format is convenient for collectors who save plate blocks, it also reduces the scarcity of the blocks and diminishes their potential value.
Consider that less than six years ago the 29¢ Thomas Jefferson stamp (Scott 2185) in the same Great Americans definitive series was issued in panes of 100 stamps with a single plate number in one corner. That single block made up just four percent of the full pane.
On the Lila and DeWitt Wallace stamp, the four corner plate blocks make up 80 percent of every pane.
Collectors who have pursued plate-block collecting for years continue to enjoy their specialty, realizing that most modern plate blocks will never appreciate considerably in value.
Value is not always the motivation for building such a collection, however. The reasons are based much more on the challenge of accumulating the blocks that one seeks and the satisfaction of building a collection that best suits the collector.