First D2 Was Sold in 1974
The first Rexair-Rainbow with the PN option was the model D2, which is just the model D with a provision for the PN on its motor assembly. The original model D was produced from 1960-74, and the D2 replaced it in January 1974.
The D2 was produced until December 1979, at which point it became the D2A... which combined the motor unit of the forthcoming D3 into the D2's bodyshell. However, were there any non-"A" D2s that got the chocolate brown color instead of the original copper?
With the mid-1980 introduction of the (all-plastic!) D3, Rainbow switched from the Eureka PN to one made by Whirlpool, which under Rainbow was sold as models R2800 and R4375. The D3 was replaced by the D4 in 1985.
I'd think the Eureka PNs Rainbow used were all of the Vibra-Groomer I type and I don't think they went with the VGII version? That is, if the VGII was introduced in 1980 along with the original D3.
~Ben