Offline
I found this while looking around. Claims to be a steel tube with no optics or lenses. Could possibly be made with copper plumbing items from the hardware store.
https://www.cowanauctions.com/lot/left-handed-contemporary-flintlock-bench-rifle-3917069
Offline
I think those were a kind of non-optical scope sight. I believe there was a cross hair or blade sight.
Offline
My thoughts too, might be a fun project!
Offline
Yes it is a tube sight. I have an original picket ball rifle from the late 1850's with one.