| 968 / | HD | HOROLOGY |
| 831 | DD | APPARATUS FOR MEASURING UNKNOWN TIME INTERVALS BY MECHANICAL MEANS [G04F 7/00] {3} |
| 833 | | .~ Using a mechanical oscillator [G04F 7/04] {2} |
| 834 | DD | .~.~> Running only during the time interval to be measured, e.g., stopwatch, etc. [G04F 7/06] |
| 835 | DD | .~.~> Watches or clocks with stop devices, e.g., chronograph, etc. [G04F 7/08] |