Hi,
I came across these stamps recently and thought they looked odd.
Both sets are complete.
What I notice is the paper looks very different compared to normal versions of the stamps. The paper is quite translucent, and looks darker compared to the normal white paper. It almost reminds me of pelure paper of some of Latvia's early stamps.
In this first picture is shown all the stamps. All seem to have this different paper, except the top left (green 9 pies) one. It seems to have the normal white paper. It also has a visible watermark. All the rest don't seem to have a visible watermark, except for the pink 1 anna on the left, where some white paper appears in the right selvedge, and I can see part of a watermark.

Here's a close-up of the pink 1 anna with whiter area in the selvedge

Here's a comparison with 2 of the 9 pies stamps. White paper version in back and translucent version in front. You can see the central black design through the translucent version.

Here's a different comparison between the white paper and translucent paper versions. White paper in front, translucent paper in back. It really show the color difference.

Any ideas about this paper difference?
The paper color seems continuous on each stamp, except for the pink 1 anna that has whiter paper on along the vertical strip on the selvedge.
I see in my Scott catalogue a note at the beginning of the Official Stamps section that mentions, "Two printings of Nos. O1-O10 exist. The first printing has brownish, streaky gum, and the second printing has clear even gum."
The note doesn't seem to apply to these stamps (#26-29, O25-28), but it was the only note I saw about different printings. All the stamps are MNH/don't appear to have any gum issues. There are notes under the listing indicating that these stamps do exist 17.5 x 17 instead of perf. 13, but these stamps seem to be the normal perf. 13.
Could they have absorbed something? I don't know, but they caught my eye as definitely looking different!