Thanks for posting this. I know it might not of been what you would have liked. However, I've found several of these at an old 1800's housesite and could not figure out what they were. Now I know. Again, thank you!!!
In the first picture on the right side there is a depression. On the flat area just to the left of the depression there is a letter denoting the musical note that the reed represents. I can see the letter stamped in yours but can't tell exactly which note it is. I think the top of the letter will be at the right side so that if you rotated the picture 90 degrees counterclockwise, the letter would be upright.
It's a Pump Organ Reed, my digging buddy and I were just talking about why and where we find them. It's still a mystery but at least we figured out what they once were.
Don't worry, I thought they could be flip up sites the first time I found one too.