A six-feet wide carriage (about 183 cm, nearly 2 meters!). I'm imagining that needs a very solid carriage escapement for such a large moving mass (or move very slowly).
Will also take up some desk space, six feet either side of the machine.
Can't quite imagine how it would be to index a six-feet wide and 12-feet long sheet of paper. Unless very thick card, surely this would crinkle and crease at indexing. Maybe the trick was to keep it rolled up inside the carriage, the picture seems to show this.
Regardless the practicalities, I'm guessing it didn't catch on in a big way in drawing offices. If there was a benefit, it must have been for a very niche application. I've myself worked in a drawing office. Rows of drawing boards and some colleagues still wore white coats too (not only for show, useful when you're inking a drawing or filling your pens).
Lettering and dimensioning a large sheet is quite fast, even when using a character-template for lettering. Only if there would be reams of text on a sheet can I imagine that typing could be faster. And then it would be easier to type the paragraphs on a regular sheet and paste it onto the drawing using photographic copying. More common is to keep all the text (instructions, bill of materials, etc) on separate regular size sheets. Niche application then, needing many variable typefaces (defense plans).
Anyways, a very wide carriage that :)
Maybe widest ever?