grading stamps

Here are some ink stamps I made for TAs to use when grading projects from CMU's 15-410, Operating System Design and Implementation. They were cut from a 1" square bar of 6061 aluminum, to 0.95" square and 2" length. The finger indentations were cut with a 0.5" ball end mill, with a tilted head to avoid the poor finish from the center of ball end mills. The engravings and faces were all done with CNC, then everything was sanded with a nondirectional finish.

What the stamps mean (clockwise from top left in the top picture):

Although the metal faces do not hold ink as well as rubber ones, they do make a nice satisfying thunk when used.