
Awg you all got me blushing, now.
Those who know me physically will add “Nevermind, we know we can’t stop you talking… and you can use three extra kilos!” 

Sorry, I really have too little experience with harmonicas. All I’ve tried (and disliked…) are your basic diatonic Hohners, and these had much less resistance than the Accordina. On the latter (all I tried is a vintage, metal one, see below links), I’d run out of air later than with a standard high whistle. I liked the back-pressure too–made it very reactive to tonguings, with a wide variation of attacks. I guess you could get the same “ragged” effects as with a push-pull squeezebox, just by tonguing.
The name is Accordina. They were originally invented by the Borel company, along with a piano keyboard twin, the Clavietta.
With this revival, the sound is different because the wood box has a “cassotto” effect. Also, the reeds are harder: steel, “fatto a mano”.
The idea was to give it more back-pressure, and save gas so you can take advantage of the “C” system keyboard, i.e. full extended chords.
For the same reason, the air duct/chamber is as small, rigid and short as possible; this eliminates the sluggishness of the bigger Melodicas, and allow not only triple-tonguings but even tongue-flutters or growls.
While expensive, these cost a fraction of a melodeon of similar quality.
Also the choice of keyboard (and single reeding, “dry”) makes it extremely compact: you can tote one about anywhere. Try and get a smaller wind with over three octaves (plus chords!). Some smarties will chime in there’s always a small clarinet. Well, before I can blow one of these throughout 3 1/2 octaves, fast, chromatically AND in tune, well…

This month, I should be finally able to try out a Vibrandoneon, same system but with double reeds (bandoneon tuning plus two single-voice registers).
For those interested in these “mouth-blown harmonium” family, see http://akkordeon-maurer.de/documents/d/Accordina_Blasakkordeon_Clavietta_Claviola_Melodica_Vibrandoneon%20.htm#Clavietta
Sorry, this time it’s in German. You’ll see it’s nothing new, and the Melodica isn’t the sole one with popularity. What are rare are those with the “accord” (chord) type keyboards.
Also the original Borel Accordina, cheaper than the wooden redevelopment opening this thread is manufactured again in France:

See the manufacturer http://www.accordinas.com/accordina_en/accordina_jazz.htm?en_accordina
also http://perso.club-internet.fr/manoury/index.html/accordina.html
This dealer here is in Germany, but talks/writes three languages and can supply the accordinas too. Fine guy, who lives from acoordeon, piano and harpsichords tuning…
http://akkordeon-maurer.de/accordion_workshop.htm
P.S.: Interestingly, the two persons linked above share a special interest for bandoneon music, especially Piazzola’s.
Well, I guess I didn’t really chance upon them… 
Btw, the same people who do the “Vibrandoneon” recently introduced this, simply (?) labelled “Astor” http://www.accordions.it/bandoneon.html