The quantities issued numbers are in most cases rough estimates, in some cases very rough estimates. Some would argue that the
numbers are so speculative they are meaningless, and while there is some truth to this argument, the numbers do at least provide an upper bound for
a particular variety and in most cases give a general feel as to the scarcity.
It must be said that quantities issued for stamps are not as useful as quantities issued for coins and currency, since once the stamp has served
its purpose it has no intrinsic value other than as a collectible, and most stamps have been discarded or lost in time for that reason.
Many of the estimates are based on the number of impressions made of a particular plate. According to Baxter1, very few plates made as many as 40,000
impressions before they wore out, with the average probably closer to 20,000. Since most of the early plates had 200 subjects, the 20,000 plate impression figure would translate to
4,000,000 stamps over the life of the plate. Stamps were produced on an as needed basis and for many of the higher denominations nowhere near 20,000 sheets of stamps were printed and in many
cases, if the stamps were not sold, the government destroyed them.
Quantities printed of various varieties of a particular issue are determined by the number of positions of that variety on a particular plate multiplied by the
estimated number of impressions of that plate.
By way of example, the estimated quantities issued for the various type I stamps of the 1851-1857 one-cent issue were determined as follows. An initial estimate of
the number of printings was made of plate 1 early, for types I and Ib, and plate 4, for types Ia and Ic, based on production records. This estimate is between
30,0002 and 35,0003 for plate 1E. Since there is only one position on plate 1E that was type I, 7R1E, it is estimated that only 35,000 copies of
type I, Cat. # 5, were printed. Since six positions on plate 1E were type Ib it is estimated that 210,000 (6 x 35,000) copies of type Ib, Cat. # 5A, were printed.
Similarly, it is estimated that a little over 6,000 printings were made of plate 4 that were subsequently issued imperforate. Since eighteen positions on plate 4 are type Ia,
a rough estimate of about 110,000 copies of the imperforate type Ia, Cat. # 6, can be made. Further, eight positions on plate 4 were always type Ic while two positions
were sometimes Ic and sometimes IIIa as the plate wore over time. These two “swing” positions are 41R4 and 49R4, with 41R4 being type IIIa for most of its life and 49R4
being type Ic for most of its life. Thus a rough estimation of nine type Ic positions on plate 4 is made, yielding an estimated total printing of between 54,000 and 60,000
(9-10 x 6,000) type Ic imperforate stamps, Cat. # 6b.
Finishing up the type I one-cent stamps, it is estimated that less than 17,000 printings were made of plate 4 that were later perforated, yielding about 300,000 copies
for the type Ia perforated stamp, Cat. # 19, and about 150,000 for the perforated type Ic stamp, Cat. # 19b. Note that the total number of plate 4 impressions, issued both
imperforate and perforated, is about 23,000, which is close to the average number of plate impressions possible as estimated by Baxter.
The point of this exercise is to show how the quantity issued estimates for varieties have been derived. It must be remembered that the number of surviving stamps is much smaller
than this, often less than half a percent and possibly much less. As time went by, and particularly as the Bureau of Engraving and Printing took over, the record
keeping improved and more accurate estimates can be made, but again the accounting is muddled by the fact that the Bureau did not make distinctions between watermark types
or perforations when quantities issued were totaled and these distinctions are critical to philatelists. The reader should keep in mind that the "quantity issued" numbers for
many of the regular issues is nothing more than a very rough estimate and the number of copies still in existence only a tiny fraction of that rough estimate.
1. Printing Postage Stamps by Line Engraving, by James H. Baxter - APS Publisher, 1939
2. The Postage Stamps of the 19th Century, Volume 1, by Lester Brookman (1966)
3. Linn's U.S. Stamp Facts 19th Century, published by Linn's Stamp News