I found those 2 but Im not sure if they are good or not.
1. BRAND. If it's not a Yahama, older model Selmer (the new one's quality is not as great anymore), or a Jupiter (I've never had any experience with one but I've heard that they are good), then it is a cheap knock-off brand from China, that is useless.
2. PRICE. A new alto sax should be about $1000; $200 new saxes are knock-offs from China. Used is generally around $500 if it is a reputable brand (see above), but it varies on the condition of the saxophone and what extras (neck strap, swab stick, reeds, etc.) it comes with.
3. PLAYABILITY. If when an experienced saxophonist (if you've never played sax before) can't play it without squeaking, then it is a knock-off.
