Very cool looking guitar! Congrats! I would think the "S" serial is probably for Samick's Korean factory. I didn't know they still made guitars in Korea as most seem to come from Indonesia. But the style of the serial number looks like Samick to me.
It's good that you didn't thenIt's really unkind to refer to that as the "duck in a power dive" inlay.
That's what I thought as well, but also didn't think they still made guitars there.
The other possibility would be SPG Musical Instruments Co. (Sound Professional Guitar), which makes the Guild hollow body models in Korea. Just the font of the serial number on that Harmony is not anything I have seen from them, but who knows.