I suspect that this is the link to which you refer:
http://www.shopsmith.com/ownersite/faq/markv.htm
I have it because it was saved it to a document on my computer. I looked for it on the current website and was also unable to find it. I guess I need to spend more time familiarizing myself with the new website. There have been many changes.
The chart that is currently on the website is a faithful restatement of the data contained in the chart posted by JPG except that the current Shopsmith chart shows some 510 serial numbers for production year 1985 that are missing from the other chart. It is also curious that this later list of 510 serial numbers starts with serial number 000016. If my memory serves me correctly (aka - conjecture), I read somewhere that a small number of these machines (apparently 15) were distributed for evaluation but were never sold outright.
http://www.shopsmith.com/ownersite/serialnumber.htm
The later chart does not clearly distinguish the 500 serial numbers from the 510 serial numbers. Note that toward the bottom of the chart some production years (1985-1987) are listed twice. The first listing in each pair are the serial numbers for the 510 (000016-008007).
There are no serial numbers listed here for 520s.