Taylor's Spencer 56-50... rear sight, thoughts?

I just got my Taylor's 56-50 Spencer carbine. It's a safe queen, idk if it's been shot.
Low serial number.
Here's my question;
Is there supposed to be a rear sight with the ladder down? Usually the answer is Yes.
All she has is a mostly flat piece of blued steel with no notch.
The ladder, of course, has a notch at the bottom, the notch on the adjustable ladder, and a notch at the very top of the ladder.
I find it hard to imagine a soldier had to flip up the ladder to use the sight. He'd never remember that when lead was in the air.

Yes, I've looked at the SORI on the SSS. The most recent info there is circa 2016, most from the early 2000's. And I saw nothing about the rear sight, other than someone was selling aftermarket ones 15 years ago.
The Spencer played a large role in the ACW and the conflicts after it, why I placed the query here.

Thanks all.