C90 Engine Birds?

Probably a stuck piece of paper, or something similar
but I thought this was interesting. The pictures show a
"normal" C90 beside my suspect version. It looks like the blue
color bled a little in both versions, but the right-hand
stamp has a distinct grouping that looks like a pair of birds
ready to hit the left engine. I thought it would be interesting
to post.

Those stamps were notorious for bleed through of the red and blue colors. You can see other examples in these stamps, such as the left part of the top red stripe where the blue color shows through.

What has always intrigued me about these stamps is what is with the left globe as shown in your blow up example? It seems as though there's a body of land in the middle of the Atlantic Ocean! Why is it there? I've always chalked it up to be a printing anomaly, but it sure looks odd.

I think the unknown land is supposed to be a lighting effect
and nothing more. And, yes, it does look like color bleed-
through, but I thought the actual shape was interesting.

I also did note that the stamps are noticeably different heights,
but probably within manufacturing tolerances.

Yes, that's an issue with the perforator.