That weird looking breech profile is the way crescent made the .410s. Perfectly safe and sound, unless they really took a lot of metal off when rebluing. I doubt that it has thin walls from polishing the tubes though. Ive got to say that its one of the finest crescents Ive ever seen. Sure wonder what that reserve is and who did the upgrade. The uncheckered butt makes me wonder too. Maybe the owner thought the wood looked better?