Originally Posted by
icemilkcoffee
I agree with your guess- it's got to be an internal wedge seat post. In a way- a wedged seatpost would solve a lot of problems. It's common to see all kinds of cracking issues around that rear seat bolt and the slit in the seat tube.
This did not let me rest and I revisited the pics. I tend to see a few pixels around on this pic which might be a screw or just a reflection on the chrome. You know how human brain works if you want to see something you might see it even if its not there..... so it can be something or nothing. I guess this will remain a mystery for a while.
Normally I try to post good quality (and high res.) pics but in this case the bike jistified to work from whats available.