The frag at upper left in the photo is from the nose portion of a 3" Schenkl Case-Shot. Your guesses about the other frags are correct. More specifically, the 12-Pounder roundshell frag is from a Case-Shot. (In 12-Pounder caliber, Case-Shot shellwall is about .45" thick, and Common-Shell shellwall is about .70" thick... and of course, the fuzehole area is thicker than that.)