As implied in one of the previous posts, agathis is considered the "poor man's mahogany", much like poplar is the poor man's alder. Generally, I've seen agathis bodies on Squier's Gibson/Guild knock-offs. Whether agathis is not as desirable tonally, or it simply doesn't have the exalted reputation of mahogany (guitarists can be very close-minded about what's in their guitars), I'm not sure. But I've heard good things about the Gibby/Guild-style Squiers so it may be an underrated wood.

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General of the Grammar Nazis, 41st Exploding Toad Division.