Nikko made a na 2000. If that's what it is its worth about $25. I would pass on your friends amp regardless. When there's no information at all online for that unit, it's not worth pursuing.
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As Donjr indicated, Nikko made a model NA-2000 integrated amplifier (around 1984). Google "Nikko NA-2000" and you'll find some photos of it. If it looks the same it is probably a badge-engineered version of the same thing (i.e., the same thing under a different name).
According to an older bluebook I have, the Nikko NA-2000 sold for $330 in 1984. One recently sold on eBay for $70. Another one that had various problems did not sell at $10.