I see a stepthrough frame dating from the 70s or earlier, based on the cottered cranks.
The rims have a dull sheen to them which suggests aluminium alloy not the period steel. Test with a magnet, and check if the tyres are 27" / -635 size, or have been swapped for a more modern -622 size.
E.J. Korvettes was a department store in the US from 1953 to 1980, and Power King seems to be their house brand.
Do a google image search for "korvette bicycle" and browse a lot of results.
Here's a 1978 power king 10speed http://oldtenspeedgallery.com/owner-submitted/john-hs-1978-e-j-korvette-power-king-10-speed/
The contrary point is the "made in taiwan" wording, which implies later than 1970. Taiwan was only coming into its own as a manufacturer in the 80s.
You obviously have a bunch of bikes based on the background. I'd suggest getting a cane or wicker front basket for the PK and use it as a shopping bike.
None of your other bikes have mudguards - this one has full-length guards and could be ideal as a rain bike with the internal hub and chain guard.
As you've noted, the bearings are working fine 30-40 years later, and it appears to be a great bike. As they say "the correct number of bicycles to own is N+1"