Into the Deep Blue
The higher denominations (2pi, 2 1/2pi, 5pi) for the 1872 & 1874-75 printings pose their own identification challenges. But unlike the preceding post in this series ( 20pa, 1pi), there are no lithographic stamps to consider; They are all typographic.
Alas, the color differences between printings for the 2pi, 2 1.2pi & 5pi, although there are indeed some, are not enough for absolute identification. Therefore, one may need to lean on careful perforation measurement as a primary tool for identifying the printings.
For the 1872 printing, all three values considered here come as Perf 13 1/3 clean cut, and are not found in this perf combination for the 1874-75 printings. For the 1874-75 printing, all three values considered here come as Perf 12 1/2 rough, and are not found in this Perf for the 1872 printing. In addition, the 1874-75 printing has a Perf 13 1/3 X 12 1/2 rough for the 2pi value which is exclusive to the printing.
Then there is the general differences between 1872 and 1874-75 printings which are helpful (Clear impressions vs blurred impressions; Thick Opaque paper vs Thinner paper; Clean cut perfs vs rough cut perfs).
Unfortunately, the common 12 1/2 X 13 1/3 Perf is found for all three values considered here in both the 1872 & 1874-75 printings. That, clearly, will make it more difficult to identify these Perf stamps. (Perhaps "clean cut" vs "rough" perfs might help: not so much - see comments further below.)
Fortunately, Peter A.S. Smith (Egypt: Stamps and Postal History: A Philatelic Treatise, 1999) points out some constant changes seen in the plates between the 1872 & 1874-75 printings that will be most helpful indeed.
Lets begin, but if you haven't already read the preceding blog posts in this series, you should do so now, as much valuable information resides there.