| 400 / | HD | TYPEWRITING MACHINES |
| 679 | DF | MEANS AUXILIARY TO TYPEWRITING FUNCTION {12} |
| 689 | DF | .~ Means for muffling typewriter noise {1} |
| 690 | DF | .~.~ By sound-barrier enclosure for typewriter (e.g., by sound-absorbing material) {3} |
| 690.3 | ![]() | .~.~.~ With externally protruding operating means |