Can you find unfindable song by sample?

I doubt the keyboard sound is effects - Unless they have a really funky FX box (Electric Mistress) or a high end Electro Harmonix. Newer custom boxes over the last ten years can achieve this sound, but its very rare to hear it used so primitively.

Doesn't sound like **most** Korgs - but it could be a Korg 770 as they had the wobbly voltage controlled dual oscillators and some nice ring modulation. I don't recall the generated tone being as smooth as this is, nor the filtering making it this way.
(pull up Human League, Heaven 17 and you'll hear how the Korg 770 is usually used for more "bouncy" tones.

Doesn't sound like any out of the box Roland synthesizer I know of. If they had access to a a Roland 100M modular system (which could make the sound) they would likely have a more complex or distinctive sound.

Possibly a Moog, but they had so many easy to achieve fantastic sounds, that I doubt a band would use a "sub-par" sound like this song has, compared to what the Moog does out of the box.

I never played around enough with the older ARPs like the 2600 and Odyssey, so not sure if it could be that. Unlikely to be an Oberheim synth.

Synclavier, PPG, Kurzweil or Fairlight CMI could make the sounds, but again, these had so many other options that usually bands would make the sounds really worthwhile in their tone.

Rhodes Chroma Polaris could make the sound with just a few slider moves, but here again you are looking at polyphony rather than a single tone.

Yamaha sounds were far too clean.

Sequential Circuits is right on the mark for this kind of sound. There is no polyphony, (which most bands would use if they had it, and for this song you would hear the release between notes, instead of just attack, decay, sustain and then switch to new tone). That rules out the Prohet 5/10.

So that leaves us with Korg 770, and Sequential Circuits Pro-one as the likely keyboard if it is indeed an early band.