Thanks for your responses, Huskyvacs, Brian, and Billy.
I ran across a 1975 ad that included the Model 2036, which matched the details of the poster. It was produced from 1975-78.
This is an example of Eureka's inconsistent model numbering: 2015, 2025, and 2036. One would've thought the last would've been 2035; which I believe was a commercial that WAS consistent with the numbering of the heavy duty Models 2045 & 2055.
This leads me to think that different design teams were in place, and their communication and/or coordination was lacking. Of course, they would never have guessed that any consumer would notice or care; particularly an enthusiast or a collector! Ha