The Zephyr has gone through many iterations from its inception in the 1930's. The best models are from the 40's and 50's before the release of the Super 20. They include the 3-loop neckstrap and the double-socket neck. You can also tell the later horns from the early ones by noticing the low C# valve - it is more on the outside right side of the bell, just like in most late-model saxes, instead of on the inside, as in the earlier models. While the Super 20 can costs upwards of $4000, you can find a late-model Zephyr for under $1000.