The seal is impressions in the paper. It is harder to see in the scan. But it is there if you know where to look. I can see it. Polarik acknowledges that it is there.
I know and described exactly where to look. Based on the Factcheck photos, it should be right above the blue/purple date stamp, which is reversed because it's on the back. I don't see it there, or anywhere.
Do you have a link to where "Polarik acknowledges that it is there"?
Here is another Hawaii CoLB. As you can see both the fold and the seal are easily visibile.
It's little lower and farther to the right than where the "Seal" appears on the "factcheck photos".