From the time of the Blickensderfer onwards, various portable typewriters had been made of just about every size and shape profile one could imagine.  Many that were attempts at the smallest possible machine failed miserably; they could not be made sturdy enough.  Generally the trend was toward larger and heavier machines more nearly equal to standard typewriters in feel, quality, sturdiness and output.

That changed in 1935 when the firm of Paillard, located in Yverdon Switzerland and who had been manufacturing the line of Hermes standard and portable typewriters for some years introduced a new design - the Hermes Baby.  This new design was exceedingly flat, and very light but quite sturdy.  (Jim Dax's Hermes Featherweight, a super-light machine is seen at left.)
Had the machine failed, it would be only an interesting footnote among collectors.  It did not fail, though; it took off immediately in sales.  (Hermes Baby at right, Will Davis collection.)

What was significant to the customer was the fact that the machine was easily the most transportable machine extant with four-bank single-shift keyboard; it could be carried anywhere by anyone and used anywhere.  It was also very sturdy and reliable.  What was significant to the maker was that it was not only an untapped market which had been opened up, but a market actually willing to pay a premium price for such a machine ... which in all likelihood was LESS expensive to make than larger machines, giving a greater margin of profit.
Naturally, the well-known Corona division of L. C. Smith & Corona Typewriters Inc., who had been in the portable typewriter business longer than anyone by this point probably knew all too well the concept of price premium for convenience and portability.  It is no surprise that it was this company that produced the first major response when it released the Corona Zephyr in 1938.

The Zephyr was much like the Hermes machine in overall size and shape, and like it weighed under ten pounds in case.  It had a different type action from that of any other Corona machine, but then again so did that of the flat Hermes differ from any other previous Hermes machine.  Neither machine's type action was as good as that of larger portables, but again neither felt weak, cheap or unresponsive.  A new level of design had been reached, which would eventually take over the portable typewriter industry many years down the road.
On the right, the type action of the Zephyr and later Skyriter.  Note that the design doesn't use key levers that run into the machine; they don't even make it as far back as the type basket.  Most large portables, and standards, had key levers (yellow here) that ran all the way to the REAR or at least part-way.  Instantly the reduced manufacturing expense is obvious.  Hermes design similar, not identical.
It was obvious then, to anyone familiar with typewriter manufacturing that such a machine could be used by anyone -- even if they didn't specifically NEED a typewriter that could be used on an airplane or train -- and that making such machines and selling them at the premium price that such portability coupled with ruggedness allowed ensured a good profit.  British Typewriters, Ltd. of West Bromwich, England took up license production of the Hermes machine very shortly after its introduction and continued making these machines for many years.  Empire Portable, at right, is one of these early units (Will Davis collection.)

This field of "flat" travelling machines would grow incredibly but even more important to the engineer the concept of what I refer to as "front mounted type bar mechanism" or design without long key levers, where all action takes place near the front of the machine, would take over even more; we thus must recognize these two early machines (Hermes, Corona) as the beginning of the development of what we might buy today, brand-new, in 2007.