I have good reason to think that this catalog sheet dates back to 1976, while the 1100 Line catalog sheet posted a few days ago dates back to 1975.
Here's my rationale... the 1100 line was introduced in 1975. The previous 1100 line catalog sheet featured masks numbered from "PSM1-3" with the 1100 line POTA masks being numbered "PSM4-7". The catalog sheet in today's post has the addition of the 1100 line PSM8 (Fly), which leads me to believe that it was released at later date than 1975. Actual multi-page DPS catalogs began being released in 1977, which would leave 1976 as the natural year for this catalog sheet to fit into. It's possible that this is one of the very last single page catalog sheets to be released in the 1970s by Don Post Studios.
Image Source: The Maskahuna