That's a rare sight ... a CB with a PN. Congrat's, Keith. That PN-2's polished aluminum looks so stunning with the CB's stainless steel!
Is that a PN-2 or PN-4? The reason I ask is that the PN-2's elbow color changed from jade to ivory with the Super J's debut in 1975 (the PN-4, introduced in 1976, only had an ivory-colored elbow and wand sheath).
I'm pretty sure that the teal-blue CBs were made until 1977 or 1978 to more easily distinguish them from the honey gold CBW and CW wet & dry canisters that were marketed for a very short time. So if you have a PN-4, it may be one from the last iteration.
Fyi, Here's some other info. I found in a service manual:
... the new-style 3-pin plug on the Model CBs was implemented in August 1975
... an added feature to the Model CBs [with the Super J motor] was a 1/4" diameter vent hole which was drilled just above the Electrolux brand plate on the rim of the motor housing. This was in case one vacuumed powdery dust or lint (which clogged the bag and caused motor over-heating) and didn't want to stop in the middle of a session to shake out the bag. A plug was inserted during regular operation (part 13150)
... in the past it was possible that the power nozzle receptacle might not line up with the hose when the top cover was reinstalled after emptying the dust bag. As of now (February 1977) all CB cleaners manufactured have a new, positive alignment latching system which allows the top cover to be installed in only one location on the cleaner body.
... (Feb. 1977) a 2 3/4" adapter cord (no. 42112)--used as a retrofit for attaching the PN-4C (with a 3-pin plug) to CB cleaners purchased before August 1975 (with a standard receptacle & hose cord)