I'm so glad to see this thread exists and is still active!

I own a Tokai/Sigma SBG2-6, no serial I can find on it. As my second-ever guitar, I have a real fondness for the feel and the sound of it!

I've seen a Sigma CS-3 (Classical, spruce(?)) locally which looks to be in fine condition, MADE IN KOREA with serial #114740.

I'm concerned because I can't find any reference to the model in the Blue Book of Acoustic Guitars I'm looking at
on Google Books. It skips right over CS-3 to -4 from -2!

Any info someone can share? I'm mostly interested in mfg. year. Thanks so much!