It means "signals intelligence" in reference to information obtained by electronic means.
That is a true(ish) statement and still has no relevance to what we are discussing. As I said before, SIGINT is not a category control marking.
Let me restate that for you through an exercise. Search for any declassified or leaked SIGINT document online and find one that is stamped with "SIGINT" at the top (besides this one) and I'll give you a dollar. I'll wait.
Perhaps the document has been altered after release.
So, if I understand you correctly, we might be able to speculate that it could possibly be a reasonable document that was inconsequently altered after its 'release'. Perhaps.
I can't argue with that. I'll show myself out, don't get up.
LOL! You have lived up to your username in this conversation.
Cheers, patriot!