Is the Document you received different from the PDF ad we each have? If so I would love to see it. I still believe this was made early on for the 10E. First it is pictured in the ad on an early 10E as you noted with the first fence and also has the early trunnion. Second it's part number 123-1X is from before all the part numbers changed in November 1951. If it had been made only in the late 10ER production it would have a different part number. My guess as to why there are not very many out there is these were an additional item and Magna soon came up with the more common arm the attaches to the table post with the screw that raises and lowers it. That was most likely cheaper to produce and is simpler to use with the same effect. It quickly became a standard item on the Shopsmith which is why so many have it. As to the quote from the Ad we have in PDF form...
Although it says "to move the table up and down" I'm not sure they were talking about the Shopsmith but may be referring to other tools. Either Table Rising Assembly depends on the table being moved close to the correct height than set the post on the early one or the arm on the later system and turn the screw adjustment to set the correct height."Table is raised quickly to a position near the desired setting. It can then be raised by a screw adjustment to the precise setting required. No slow, tedious cranking to move the table up and down, but precision where precision is needed."
No slow, tedious cranking What does that mean if this is the first table raiser?
Both set the table to the "precise setting required." Just my feeling on the subject.