At the very bottom right there is a reference to 0782100M

Googling that returns below which also says (maybe infers?) the brochure is from 1982.

https://www.computerhistory.org/collections/catalog/10264626...

I had considered that, but noticed the price and as classichasclass points out in a reply to me (https://news.ycombinator.com/item?id=43949843), $595 was the intro price. They're also comparing against the Atari 800 instead of the 800XL, so that's another piece of evidence. The 800XL was released in 1983.