Trying to determine what clock got the flip clock craze going, therefore, can be very challenging. However, piecing together what we know factually, and adding a little supposition, I think we can come to a reasonable conclusion.
We know that the vertical/upright cylinder flip clocks, most often referred to as the Plato Clocks, were the first flip clocks and they arrived on the scene in the very early 1900s (hard to believe, but true). As quickly as they showed up, they seemed to have disappeared - evidently, it just wasn't their time.
In the mid to late 1930s (about 1937-39) the New Haven Clock Company produced two varieties of flip clocks, but possibly due to the Great Depression, then onset of World War II, the time of the flip clock had not yet come.
Now many flip clock fans may have heard of Japan's first flip clock - the Copal Caslon 101 - designed in 1964 and released to the world by the Copal Company in 1965. Also, the Solari Udine company, makers of split flap information boards in train stations and airports produced marketable flip clocks in 1966. Not to be outdone, about this time (around 1967), the Howard Miller clock company released two varieties of flip clocks as well.
But many do not know or appreciate the story of a now defunct German Company that have actually brought the flip clock back to life and got the world flipping in time for the decade of the flip clocks - the 1970s.
The clockmakers, Uhrenfabrik Laufamholz Köhler & Co brought back the historic Plato clock in a more ornate style as early as 1953. In addition the the upright, vertical models they also produced a horizontal cylinder type clock, that appears to flip clock fans, basically, as a modern flip clock. To my knowledge there was no model number assigned to these clocks and they may have been designated as the "horizontal model." These earliest clocks have the trademark "Köhler" on the mechanism. Later the rights to produce these clocks were sold to Josef Mergenhagen, then in 1965 Mergenhagen's business was absorbed by Karl Lauffer Uhrenfabrik GmbH, Schwenningen, Germany, who continued to make the Plato type clocks until around 1970 it is thought. These German clocks were distributed in the United States exclusively by the Horolovar Company, Bronxville, New York under the ownership of Charles O. Terwilliger. Jr.
In summary, I propose that the Köhler horizontal model flip clock from 1953-1964 woke up manufacturers to the viability of the flip clock which resulted in the production of clocks by the previously mentioned makers (Copal, Solari Udine and Howard Miller).
Curiously, back in this time period the clocks were often marketed as the "computer age" or "space age" clocks of the future. Strange, since there were no computer parts or even transistors in these clocks. The new clocks caught fire with consumers in the late 1960s to early 1970s who had never seen such a wonder as the flip clock. To them, it was all new and modern - just in time for Apollo and the moon. They would have had no way to know that the technology they were appreciating came from way back in the 1900s and that a little flip clock that started the renewed interest, was already at least 10 years old by the time they were buying their first flip clock. But, we can't hold this against them - no internet, you know.
The Köhler horizontal flip clock - in my opinion a pivotal, historic flip clock. If the Plato clock can be called "The Grandfather of all flip clocks," then the Köhler clock should be called "The Father of the Modern Flip Clock."
ADDENDUM
Since this article was published it has been learned that the Real first flip clock was produced way back in 1894 by the German Lenzkirch Clock Factory after being invented by the famous Josef Pallweber. Making flip clock history that much more exciting. Check out the history of the first flip clock!