Actually it has never become known if this movement has been made at a Gruen facility or if someone else made it. Dr, Ranfft stated that it is based on an Ebosa caliber 94 ebauche, but I recently found out that this is incorrect.
Gruen used this strange movement which has no similarities to any other Gruen movement in their "Americana" and "Canadiana" series which were introduced in 1959 and sold until 1961. This series consisted of three men's watches, the Water Chieftain, the Sea Captain and the Water Phantom, and three ladies watches (Vivian, Rosalyn and Infanta).
The three men's watches were all based on the same movement, the caliber 100SS. This is a strange 19-jewel pin lever movement, stamped "GRUEN WATCH Co 19 JEWELS 100SS NEW YORK". It features a strange V shaped holder for cap jewels and looks very cheap. Here a photo of one of my 5 watches based on this caliber.
So it says "NEW YORK" as origin! Just something one would expect for an Americana called watch series. But has it really been built in New York? No, it might have been purchased from a New York based company, but the factory making these movements has been located elsewhere. Now, where did it come from?
Two weeks ago I found the missing link in a German horological magazine, published October 1959:
Neuer Uhrentyp der Gruen Watch Co
Anläßlich des internationalen Kongresses der amerikanischen Bijoutiers kündigte die Gruen Watch Co den Verkauf einer 19-steinigen Uhr an, die von der Precision Time Corp. in Strasburg hergestellt wird. Es handelt sich um eine Art Stiftankeruhr, in der die Metallstifte durch Rubine ersetzt sind.
English translation:
New type of watch from Gruen Watch Co
On the occasion of the International Congress of American Jewelers, Gruen Watch Co. announced the sale of a 19-jewel watch manufactured by Precision Time Corp. in Strasburg. It is a type of pin lever watch in which the metal pins are replaced by rubies.
When I read this I immediately thought, hey, this can only be caliber 100SS, which in 1959 was the only 19 jewel movement Gruen had. Bingo, the ebauche is from France, was my first thought, this is why I never found it in my Swiss sources! But I was wondering why the company had an English name and I started digging. And guess what happened? I found a trademark filing from 1954 by a New York based company called "Precision Time Corporation", this trademark was for the name "JARO". But, the article said Strasburg, so may they have opened a French subsidary building their movements? Again, a dead end, but further investigation brought up a little town in Pennsylvania called Strasburg and hallelujah, the Precision Time Corporation in 1958 started building a new factory in Strasburg, PA, for producing their own movements. In fact they started production around Easter 1959 already and sold their watches as JARO watches soon. These watches were 17 jewel watches, but when I looked for the movements of these watches, I found that they are indeed based on the very same caliber as our Gruen caliber 100SS. So the Precision Time Corporation sold it as 17 jewel movement in their own JARO watches and as 19 jewel version to Gruen. Here a Jaro movement for comparison:
And here a picture from a 1960 Jaro advertisement:
Unsure where the two additional jewels are located in the 100SS, I would have to disassemble one of mine to check, may be the balance jewels are capped?
Probably worth noting that the initial price of the Jaro watches was $14.95 while the Gruen came at $19.95. Within a year the Jaro sales price came down to $8.88, one special had been as low as $7.77. It looks like the Precision Time corporation supplied to Gruen for about one year only and sales of their own watches was not as successfull as they hoped. Their plan had been to build about half a million watches / movements per year and they also developed a ladies caliber with either 21 or 23 jewels which was sold to integrators and developed a 8.75 ligne movement which did not make it to production before the company closed the doors in 1963 or 1964 already. The Time and Micro Instruments Inc. took over the facility which as well has not been successful. Nowadays the factory building houses the police station and a library.
Anyway the riddle around caliber 100SS is finally solved. Made in Strasburg, PA, USA it has been the perfect choice for the Americana series. I think it has been a big secret also at that time this series was actually nothing else but a cheap Jaro watch and Gruen must have been very quite about it. This will also have been the reason to stamp it with NEW YORK instead of anything else giving a hint to the Precision Time Corp. It is also possible that the final assembly of the complete watches happened in the old Precision TIme Corp. facility at Long Island where they assembled watches before they made their own movements. It is also possibls that Gruen purchased the completely assembled watches from the Preicsion Time Corp,, not only the movements. But I have not found evidence for this yet.
