It is not surprising the shape evolved during 40 years of availability in the catalogues. When did the change happened? I have no clue of the date, but it probably was rather soon, as it can be deduced to the rarity of the first shape.
The original model had a full rounded air duct cover. Later, the Humanatone got a tappered cover, forming a plane whistle.
Finally, the marks evolved, and the « Other patents pending » stamp disappeared, replaced by the mention of Leech and Couchois'
About metal Humanatones, check :
- Humanatone - part I : the metallic era
- New Humanatone ads
- The Two metal Humanatones
- Another metal Humanatone
- Humanatone boxes
- Another Humanatone box
- Humanatone: A very early user manual
- The Magic (Nose) Flute: only questions... .
- A Humanatone and clones chronology
- A Humanatone in 1892 ?
- Humanatone: Early promotional demos
- Another Humanatone archive
- Huma... something
- Rectification: Humanatone appearance date
- Great paper from 1903
- Nose Flute Pioneers: The Stivers - Part I
- Nose Flute Pioneers: The Stivers - Part II
- Nose Flute Pioneers: The Stivers - Part III
- Nose Flute Pioneers: The Stivers - Part IV
- Nose Flute Pioneers: The Stivers - Part V
- A Humanatone as a scientific tool
- Two other Humanatone Ads
And on later Humanatones :
- Humanatone - Part II : the Gretsch plastic era
- Humanatone - Part III : the Gretsch metal era