It is believed that a master die was transferred to five separate transfer dies, one for each denomination. These transfer dies were then finished by adding the value inscription before being transferred 100 times - in 10 columns of 10 rows, to the printing plates.

The art of laying down the individual images had not improved much since 1856. Some stamps are placed far from their horizontal neighbors, while others actually overlap, making it impossible to cut vertically between the two stamps without producing at least one with one or two margins cut away. Both the horizontal and the vertical distance between stamps vary quite a bit, but the vertical distance is always the largest. It is quite common to see Eagles with large top and bottom margins, while the horizontal margins vary from cut in to perhaps 1 mm or more.

Veracruz, ocho reales pair.

There has been much speculation about the material used for the printing plates. Some believe that the early plates were made of copper, since it is a soft metal that will wear out quickly, as shown by the stamp images over time. The later plates may have been made from a harder and stronger material. Brass has been suggested, but I believe steel would be a much more likely material, since brass is quite brittle. It appears as if the early plates were more prone to develop cracks than the later plates.

The 100 images were surrounded by a frame line, just as the earlier issues. However, these frame lines are somewhat elusive - I have not seen nearly as many on the Eagle issue as I have on the first and second issue, for example. One explanation could be that the top and bottom frame lines in particular were placed several millimeters from the design and therefore were cut away more often than on the earlier issues. Another reason for overlooking these lines may be that the left and right lines were very close to the stamp designs and are mistaken for die marks or something similar.

Dos reales, showing bottom frame line.
Puebla, 240-1864, sub-consignment 7 to Atlixco.
Close-up of the frame line.

It is not known for sure how many plates were used to print the various denominations over time, but work by Franco Vannotti came to the following conclusions:

Denomination Number of plates
½ real 2
1 real 3
2 reales 3
4 reales 2
8 reales 2

Vannotti used the simple, but ingenious, approach of tracking constant plate varieties. The most spectacular of all plate flaws on the Eagle issue is the medio real plate I, position 71:

Medio real, plate I, pos. 71. Un real, O-flaw, plate I, pos. unknown. Close-up of the O-flaw.

Vannotti found that the first plates were used from beginning to end of the printings, and that the later plates were introduced after the first printing(s) and subsequently used until the last printings.

Dos reales stamps from Plate I (and II?) are taller than those from the later plates: approximately 25.5mm vs. 24.5mm.

  • Plate I was distributed from invoice 1 1864 until and including invoice 6 1865.
  • Plate II was distributed from invoice 154 1864 until and including invoice 6 1865.
  • Plate III was distributed from invoice 7 1865 until the end of the issue.

Plate I and II stamps supposedly have vertically ribbed paper, while plate III stamps were printed on horizontally ribbed paper. It is possible that plate III had 20 rows of stamps and thus 200 stamps per sheet.