Identifying #6
(#6 is a Type Ia)

#6 is a Type Ia design. The design on the bottom and sides of Type Ia are complete. However the design at the top is not complete, some of the top ornaments have been burnished off, see illustration below.
Type 1a can be found on eighteen plate positions, all from the bottom row of plate IV.
Notes on #6
1) There is no stamp beneath them as they come from the bottom row
2) Type 1a can be found on the perforated stamp as well (Scott #19)
3) Although the stamp can be distinguished by a broken wavy line at the top, a few of the positions have a blurred burr where the line is broken, giving one the first impression that the line is unbroken.
4)
They were only printed in the months of April, May and June 1857, a late period in the printing of the imperforate.
5)
The imperforate stamps were replaced with the perforated stamps on August 1st 1857.
6) A certificate is a must, never buy without one.
Why are there only eighteen positions?
The design of this early issue was too large to allow for the accommodation of the 200 subjects onto one plate. Therefore, each position had to have some amount of the design erased to allow enough room. These erasures accounted for the majority of the types. Eighteen positions, however, had only minimal erasure to the top of the design whilst the rest of the design was left complete
What exactly do the plate position numbers mean?
To take the example of 7RI1
7 = Seventh stamp of the 100 on the pane - this number can be from 1 to 99.
R = Right Plane - this letter can be either R or L, L representing the Left Pane
I
= Plate I, this roman rumeral can be I, II, III, IV, V, VII, VIII, IX, X, XI, XII
E= Early State, this letter can be either E or L, L representing the Late State. This letter is only appended to plate I stamps.
How many plates were there?
There were twelve plates of the 1c Franklin made, plate six was never used, probably due to it being damaged in it's creation. Most of the plates were used for both the imperforate and perforated design. Some only produced one type or the other. For instance, plate 12 produced only perforated stamps and the early state of Plate 1 produced only imperforate stamps whilst plate I late (reconstruction) produced both imperforate and perforated stamps. Plate 4 was the last of the imperforate plates to be used.
Rescources available
http://www.slingshotvenus.com/FranklinArchive/frnkln_archv_Main.html
Stanley B. Ashbrook, The United States One Cent Stamp of 1851-1857.
Mortimer L. Neinken, U.S. One Cent Stamp of 1851-61.
The Ishikawa collection: United States 1851-1857 1 cent Blue Issue postage stamps in multiples and reconstructed plates.
PLATING #6

Type 1A
The flaw at the top left inner circle is present on most, but
not all the positions.
Click here for a comprehensive, printable, identfication guide. Courtesy of Chris Biason (447kb)