Well, evidently at some point, this machine had the PN plug installed. Either when it was manufactured, or at some point later on in its life.
Many machines back then were sold with just the basic attachments, as the PN was considered "Optional Equipment", and sold seperatly. Even if the PN plug was already there.
If the Electrolux was originally manufactured without a PN plug, and the owner wanted to add a PN later, the salesman would wire the machine with the PN plug, right there in the homeowners livingroom,,and then sell them the PN, and hose cord and straps. Or a new hose with the straps already attached.
In the mid 1960s, when she had wall to wall carpet first installed, My Grandma had a PN plug added to her Lux Model E several yrs after first buying the machine.
The Salesman sold her a PN 1, and installed the plug on her Model E, and added the cord and straps to her original hose, right there in her livingroom.
Wish i still had that Model E,(gave it to a friend yrs ago),its the only basic (NON Automatic) Model E ive ever seen WITH the PN plug.