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):
- leaky faucet: memory leak
- pacman ghost: scary code (demonstrating disturbingly incorrect assumptions or ideas)
- run-from-explosion: something failed, code doesn't handle it and instead runs screaming (returns without checking)
- unlock?: forgot to unlock a mutex
Although the metal faces do not hold ink as well as rubber ones, they do make a nice satisfying thunk when used.