I had a professor that printed in like 3 colors, and each exam had a different code on it, like 'X3-67' so we thought he made several versions (of course it was

I had a professor that printed in like 3 colors, and each exam had a different code on it, like 'X3-67' so we thought he made several versions (of course it was graduate math and he told us we would all get an A in we showed up and participated so we wouldn't have cheated anyways). Later we compared our exams after the course ended (because he kept them until then and would just review the problems we missed with each of us in office hours) and they were all the same problems :)