Here are the humbucker-equipped guitars, but the differences didn’t end there.
Starting with the similarities, the bodies were again made of either Ash or Alder, again with Maple bolt-on necks andeither a Maple or Rosewood fingerboard.
For most models, the pickups were again branded “Kawai”, but “Schaller” branded units were used in some guitars (see the example on the left in the photo). These Schaller pickups were called “Golden 50 Super”, built around 12 Alnico magnets.
The models numbering was a little complex ...
If the model number ended in a “5”, it had a rosewood fingerboard, “1” = maple fingerboard.
Also, the “5” models had a tremelo unit, the maple boarded “1” models were used a stoptail unit.
The 605 had the Schaller pickups - shown on the left, above.
The 555 used 3 pickups, each individually switchable on-off (and so no pickup selector switch). This is in the middle, above.
The 505 (on the right) was the twin pickup model, with pickup selector and - I think - a coil tap switch with master volume and tone controls.
There were no equivalent 601 / 551 or 501 models.
Further down the range, the 405 (and 401) reverted to the pickguard design (as the 505) but used push/pull switches on the volume and tone controls to split the coils.
And finally, the 305 and 301 models used a single humbucker, no pickguard design.
Helpfully, the model numbers changed during the period that they were available, although not substantially. You may well come across an AQ600, or an AQ450 (etc).
You might also find an AQ1200. I did, and it’s sat in the chair on the left in the photo below!