Sorry, I had a typo in my first post. It is a 520, not a 420. (Though he also has a 1990s 420.
) As noted above, the specs match the 1985. It does have 700 wheels with the helicomatic hub. The cassette is a five speed. The paint job is a 1985, with the model number on the chainstays, not the downtube. But the serial number is an '84 number. The manual for the 1985 520 does show it spec'd out with 700 wheels.
Anyway, I'll try to work on the hub when I get back north. Though, tomorrow I'll be in the Tucson bike coop and I'll ask if they have the tool to remove the cassette.