I believe JSA made a mistake and authenticated a preprint
I hate to say this, but I am fairly confident that JSA made a mistake. I had one of these Barack Obama Senate letters from before he became President. It was received as a result of a simple email request for a signed photo. It arrived in a large U.S. Senate envelope that included an autopen signed photo, a letter VERY similar to this one, and a piece of cardboard.
At first when I received the letter I thought it might be real, but upon closer examination under a good light and magnification I could tell the ink of the signature was identical to the ink from the top of the letterhead…same exact blue and same type of ink. I could also see that it had zero pen pressure and look printed. I also recall years later seeing similar letterhead (from a different Senator) that was blank but had the preprinted signature along with the letterhead but no text. It looked like they printed up the letterhead with the preprinted signature then would add the text/body for whenever someone needed a response. There were several sheets and all were identical signatures so definitely printed.
Just thought I would point this out. I thought it was very convincing so I can understand why it slipped through JSA and they authenticated it, but just a heads up to be careful even when dealing with authenticated items. By the way, this sold for over $1300.