| 73 / | HD | MEASURING AND TESTING |
| 1.01 | DF | INSTRUMENT PROVING OR CALIBRATING {13} |
| 1.42 | DF | .~ Timing apparatus (e.g., fuse, camera, or shutter) {2} |
| 1.43 | DF | .~.~ Chronometer (e.g., clock, watch, or watch unbalance) {5} |
| 1.45 | DF | .~.~.~ Using optical sensor or element {2} |
| 1.46 | ![]() | .~.~.~.~ With sound sensor |