Double Black Seal $1 Note

Hm, that's pretty strange. I've never seen anything like this, or can take a guess on how it happened.

No books handy but I have a strong suspicion it's a fake.

Keep it though. I could be totally wrong.

I was looking at "Official Blackbook Price Guide to United States Paper Money" and can only think what 1337 said about a double stamp OR it could be a partial offset transfer. The book says:

"The most logical explanation for this error is that a sheet of paper fed into the press incorrectly became mangled or torn, and part of the inked plate contacted the printing press bed. Therefore, wet ink was left on those portions of the press bed not covered by paper. When the next sheet was fed through, it received the correct impression, plus it acquired a partial offset transfer by contacting this wet area of the press bed. Just as with offset transfers, the first sheet going through the press following an accident of this kind will receive the strongest transfer, and it will become gradually less noticeable on succeeding sheets (p.306)"

From the image you have it looks more like that because of the uniform smudges around the seal as well. This book only lists a series 1969D with dark print at VF=$60 and UNC=$175 and light print VF=$50 and UNC=$175. Since I am not a professional I go by the media and information of others along the way and suggest maybe sending it in to get graded or check your local coin shop.