| 33 / | HD | GEOMETRICAL INSTRUMENTS |
| 300 | DF | INDICATOR OF DIRECTION OF FORCE TRAVERSING NATURAL MEDIA {23} |
| 355 R | DF | .~ Magnetic field responsive {6} |
| 356 | DF | .~.~ Error indicator, preventor, or compensator {1} |
| 357 | DF | .~.~.~ Error-producting-field minimizing {1} |
| 358 | | .~.~.~.~ Adjustable positioned permanent magnet {1} |
| 359 | DF | .~.~.~.~.~> Pivoted adjustment |