The original Zephyr was simply the Voll True II with a different name. The instruments appear to be identical in all respects. Slight changes in ad copy do not alter the fact that it is the same instrument with the same catalog number at the same price.

[Later Zephyrs and] the Zephyr Special are completely redesigned instruments and the direct predecessors of the famous Super 20. The key design, previously the "Modernistic Style" that was ungrateful to the fingers, was contoured to a more comfortable arrangement. The mechanism was altered to eliminate the G# trill key and the alternate Eb fingering [i.e. the "fork" Eb]. The bell tone holes were repositioned to accomodate a faster, lighter action. The beauty of the instrument was enhanced by the addition of distinctive mother of pearl inlay on all the keys, including the palm, side and small finger areas (1).

Original Zephyr Plating Choices (1940 Catalog)
1-G Brass, Gold Lacquer
1-T Brass, Transparent Lacquer
Finish II (Silver Satin Finish, Gold Bell)
Finish III (Silver Satin Finish, Gold Bell and Trim [i.e. "two-tone gold"])
Finish IV (Gold Satin Finish, Burnished Bell)
Artist's Special (Gold -- Hand Burnished)
A Two-Tone lacquer body with nickel keywork was introduced probably around 280xxx.
A sterling silver bell was available on models from about 237xxx to 280xxx. The sterling neck was probably introduced around 200xxx with the Zephyr Special. The combination of the two is extremely rare.

Note that the "King De Luxe" finish (burnished gold with additional pearl keytouches) has disappeared and was "replaced" with the Zephyr Special.

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There are several models of Zephyr -- and I'll talk about the Zephyr Special and military models in due course:

1. Horns from about s/n 170xxx to 180xxx were virtually identical to the Voll True II.
Interesting note: I had a reader point out to me that the double-socket neck was actually introduced around 188xxx (some don't have it around this serial number), but while I was checking for this feature, I noticed something odd: the Zephyr does NOT have a "fork Eb" fingering. It's missing the low Eb vent key found on the Voll-True II and instead has a "bridge" linking the low D and E keycups. This means that the body tube of the Zephyr altos has always been somewhat different than that of the Voll-True II.

2. Horns from about s/n 180xxx and 237xxx have the 3-ring straphook and the double-socket neck.
That means that the bore of the horn was quite probably changed at least a bit at this time.

At approximately s/n 200xxx, the Zephyr Special was introduced: a horn with redesigned keywork (more rounded), additional mother-of-pearl inlay and probably a tweaked bore design. There are tons of reports that the Zephyr Special bore is the exact same one as the Super 20, HOWEVER, I've also had folks note that the bell on the ZS is much slimmer and, of course, the neck design is completely different. This tends to indicate that there are some bore differences between the S20 and ZS -- and Dr. Cohen writes that there are (see above). However, I've never heard anyone report that the ZS bore is different from the regular Z bore and I think they were.

Here's some fun for y'all: measure the bore of the Zephyr Special and compare it with the Zephyr produced between 240xxx and 305xxx and the Super 20. If all the measurements are identical, which I doubt, buy a Zephyr instead of an S20 or ZS. You'll save a lot of bucks, if you're not interested in the fancy pearls or engraving. (Do note that I've seen at least one Zephyr done-up with the additional pearl inlay, but no "Special" engraving. Some Zephyrs appeared in odd "high end" configurations, such as with sterling silver necks and/or bells, so that may furrther support the assertion that there were two Zephyr bores.)

The final oddment is that the Zephyr Special was around until probably s/n 280xxx -- my latest examples are in the 276xxx range -- and that's during the first years of Super 20 production.

UPDATE from SOTW Forum poster shmuelyosef:

I did do one verification that the silver neck on my non-Special tenor (281K) swapped with a 278K S20 that a local guy had ...
- As far as we could tell these horns were identical bore and tonehole layout.
- The bore on that tenor is 1.083" I.D. at the neck socket. A similar vintage alto (291K with triple strap, etc) is 0.954" I.D. at the neck socket.

The bell sizes (which I record for most horns that pass through here) are:
- 292K alto: 4.92"
- 281K tenor: 6.16
- 365K bari: 7.69 (the largest bari bell I have ever measured!)

3. Horns from about s/n 237xxx and 305xxx have the rounded keywork found on the Zephyr Special.
Again, I don't know if the Z bore design was changed at this time to make it identical to the ZS.

I could also put a "3a" in this mix: around the time that the Super 20 was introduced (s/n 272xxx), the wire leg guard was changed to the removable triangular guard found on the S20 and the bell-to-body brace was modified.

[from SOTW Forum member shmuelyosef]: From 275K till about 305K the Zephyrs (IMHO) are the same horn as the S20 except for the keyguards, the neck brace and octave key, and the cosmetics (pearls and key engraving). I have determined that the necks are interchangable and play well back and forth and all the keywork is identical as far as I can tell. I have played a 278K S20 vs. my 281K Zephyr w/silver neck and both I, several spectators and the owner of the S20 could not hear or feel a difference...needless to say, he paid more for his horn; we both acquired these within the past two years.

4. Horns from about s/n 305xxx and 423xxx have one major subtraction: the three-ring straphook. They gain "eyebrow" keyguards, but the double-socket neck is probably eliminated around 383xxx.
These eliminations follow approximately the same pattern as the Super 20 and Silver-Sonic. At least one poster has swapped necks from a "model 3" Zephyr with a "model 4" and found that they are interchangable -- at least, until the double-socket neck was eliminated. This indicates that, at the very least, the neck taper is identical and by extension, generally means that the bore is, too. Some, however, note that there seems to be a change in the low C# mechanism and the actual composition of the keywork -- from nickel to brass. This could have been evolutionary throughout this time.

5. Horns from about s/n 423xxx and 540xxx have redesigned keywork and no double-socket neck.
Horns produced in this era, after the Seeburg purchase of the company, can really be considered the "intermediate" version of this horn. It is my opinion that King discontinued production of the Zephyr around s/n 540xxx. I base this on the fact that I haven't seen a later horn and the fact that Seeburg did some cost-cutting and seems to have eliminated all baritone sax production at this time.

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Errata:
* People have asked me many times and here's my answer: no, there weren't Zephyr sopranos. There may be a few prototypes, though, and King may have done what Buescher or Conn did and trot out a soprano based on a 1920's design if someone special-ordered one, but sopranos were definintely not an official production model.

* Most people agree that the King Zephyr baritone was always based on the Voll True design (there appears not to have been any Voll True II baritones). Do note that the Eb vent key is eliminated and Zephyr baris gain and lose the same features at the same time as other models (double-socket neck, etc.) -- and military baris follow the same rules as military alto or tenors. Additionally:

It seems pretty obvious that there are significant changes to the Zephyr bari between 365xxx and 379xxx:
- Bell to body brace is different
- Front F was added
- Keys are nickel (or nickel plate)
[Both models] sound and respond identically (thanks to SOTW Forum poster shmuelyosef)

* There were quite a few Zephyrs labeled "US" or "USN" or some variation thereof and these are dubbed "military models". They don't seem to follow any "standard", so any given military horn might not have all these features, but here's some generalizations:

* Most have G# trill keys and Eb vent keys, up until about s/n 260xxx. This makes military horns look definitely different than other Zephyrs.
* The G# design is the more squared-off version that's found on the early Zephyrs, although the other keys in the G# cluster may be rounded (this was discontinued around 272xxx, I think).
* The engraving is different, sometimes not even having "Zephyr" engraved at all.
* Production of "military" horns continued at least until 320xxx.
* IF the Zephyr Special does have a different bore, the military horns probably used it.

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Tying this all together, the best Zephyrs are Zephyr Specials and the horns produced between 240xxx and 305xxx that have the rounded keywork, double-socket neck and three-ring-straphook. I've seen some outrageously priced very, very early Zephyrs. These horns have very similar intonation tendencies to the Voll True II (i.e. not good) and should be valued slightly more than that model. I can also assume that the horns produced after 383xxx should be considered intermediate quality horns and valued as such, due to all the changes from the "pro" model Zephyr. However, it also seems likely that the Zephyrs produced between 305xxx and the time that the double-socket neck was discontinued (about 383xxx) have the same bore as the "good" Zephyrs, but may be more machine-made, lack some features and/or have a slightly different body composition -- so, a good buy for the more budget-minded.

Do note that several posters on the SOTW Forum do contradict my statements about the decline in playability/tone of the later horns, but there are also significant amounts of posts from other owners confirming the cheapening of the Zephyr in parallel to the cheapening of the Super 20 and Silver-Sonic. NO ONE has contradicted my statements about the early Zephyrs, though.

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FOOTNOTES:
1. It is my great pleasure to say that Dr. Paul Cohen has allowed me to copy at length from his various articles. The articles I'm quoting from (the MAROON text) on this page are from:
- The Saxophone Journal, Vintage Saxophones Revisited column; "Kings All" September/October 1988
- and "Kings All"; September/October 1998 (no, that's not a typo :)

For reprints, please see the Dorn Publications website. To get Dr. Cohen's other products, please go to the To the Fore Publishers website.

As always, my additions are in BLACK text or in brackets. The BLUE text represents quotations from the thread I started on the SOTW Forum to research the Zephyr chages, called "A Zephyr Recap"