The markings/text font on the dial of your watch are very similar (the words are actually identical) to those on a Gruen I have (which is also a Precision 25 jewel autowinder), and the caseback looks identical to the one I have, which together suggests to me that your watch is from the early 1960s/late 1950s, and here's why:
The original (or "first") Gruen was broken up in 1958. An offshoot/incarnation (or "second") Gruen moved back to New York (for several decades before then, Gruen had been making watches at its Precision Factory/Workshop in Switzerland; the first Gruen consolidated all of its manufacturing into this facility in the 1930s - and only watches made in this facility had the "Precision" label on the dial - but the building is now under the ownership of Rolex) and operated there from 1958 until its failure in 1976. These two incarnations of Gruen are the ones in question here.
My particular Gruen has radium lume (as indicated by "RA SWISS RA" at the 6 o'clock position), and since radium was phased out of watches by 1960, this suggests to me that my watch was either made by the first Gruen before then (i.e. before 1958, when the first Gruen broke up) or between 1958-1960 by the second Gruen. Your Gruen, while sharing similar standard markings (wording and font styles, as well as caseback markings), does not have the "Swiss" marking at the 6 o'clock position, which suggests it was not manufactured in Switzerland. Since all Gruen watch manufacturing was done in Switzerland by the time of the first Gruen's breakup in 1958, your model, which could not have come from before the 1930s when all Gruen watch making was consolidated in Switzerland (i.e. the only other time when Gruen watches would not have been marked "Swiss"), is likely to have been made elsewhere (i.e. New York), by the second Gruen, despite being marked "Precision" as if it had been manufactured at the Precision Workshop (which is still possible; I don't know when Gruen stopped using and sold that facility, and it is possible that the second Gruen was still using it for a while).
Since the second Gruen operated from 1958-1976 and you have a photo of this watch from as early as 1967, it seems likely that your particular watch could not have been more than 9 years old by the time that picture was taken.
Hope that makes sense. For reference, I got my information on the dates and manufacturing details for Gruen here:
http://www.pixelp.com/gruen/. This page specifically indicates what happened to the first Gruen and the second Gruen:
Gruen Watch Company history: 1940-1958: WWII, Pan American, Gruen 21 (near the bottom).