Sorry, I didn't know whom to contact for this (glen, rich, jemavenger..??), so I put it here, feel free to delete the topic afterwards.
I was just crawling through the wiring diagrams on ibanez.com, and noticed the js100 and 600 DO have the coil tap. Also, they were often described on ebay with this feature. I think it makes sense now.
I think it's odd that only the cheapo and top-notch js
models have the coil tap, but I checked with the 2001 euro catalogue, and its true. The js900 does indeed NOT have it, while there is a single "JS100/1000" switching scheme. Hmm.
Another thing is, I had a js600 in my hands that was definately korean. There are still rumours of a japanese run, but the korean ones do exist.
So, a "Manufacture: Korea" would be better than "manufacture: unknown".
That's it so far, sorry for wasting up forum space.