What's the last picture? It looks like a piece of wood?
If you are planing on restoring this bike, I'd recommend stripping the paint and carefully examining all the tubes for pin holes which would indicate that the tubing has rusted through.
Tube replacement becomes expensive and I would only do that to a frame that had some historical value.
I've seen that problem on lots of older bikes that appear to have been under water for a while....
A 26.8mm seat tube usually indicates heavy gage butted or straight gage main tubes...
verktyg
Chas.