Since we have to wait for size measurement and additional photos to clarify what the letter on the shield is, I'll show you the other known variations of your friend's find. I've put a lot a research into them because they were deing advertized on Ebay as "Confederate saddle-shields." That is fraudulent. They definitely are not Military.
Also, nobody seems to be able to come up with any proff they are from the civil war era. (In my opinion, they are from sometime in the first half of the 20th-Century.)
Actual saddle-shields are flat. These are curved, to be screwed or riveted onto a cylinder which is approximately 3.0-inches in diameter. That suggested they are a motorcycle or bicycle front-frame "badge." That tube on a bicycle is usually smaller than 3"-diameter... but just to make sure, I emailed a major collector of bicycle badges. He said he's never seen one like these.
Note that the three attachment-holes on these brass shields have a solid-cast "reinforcing pedestal" encircling the hole, to strengthen the attachment area so the shield cannot easily "tear through" the mounting-screws/rivets. No saddle-shield has strengthened attachment-holes.
Here are the photos of four known variations, and a photo showing the shield's curved body. The known letters are A, C, M, and T, all of them in Old-English Script. If your friend's letter is indeed an F, that would be a fifth variation.
Important note:
The photo showing the curvature, with a US 25-cent coin for scale, is "perspective-distorted" by the depth-distance between the two objects in the photo. These shields are not 3 inches wide. The only width reported thus far is 1.6-inches, but I'm not sure of the accuracy of that measurement.
Note that the background on three of them is raised overlapping circles, and the other has a checkerboard background.
Three of the variations in the photos show gold-plating.
I'm posting all of this information (and the photos) in the hope it will prompt somebody who knows for certain what these things actually are to step forward with solid proof.