Toward the end of Timex mechanical watch production there were some models that seem to have been manufactured without the production numbers printed on the edge of the dial. Yours might be one of them. Actually Timex continues to use their Philippines factory to produce their watches. I was always of the opinion that the Philippines facility was the locationi where the finals runs of mechanicals were made.
Since the last years I've found printed on dials was in the 1980's and it seems that Timex ceased all production of mechanical watches by the early 1990's, I'd say your watch is a 1980's version.
I wish I could be more specific but that's the best I can do. One thing is absolutely certain. Your watch was not made prior to 1980 since all Timex watches from the early 1960's to the early 1980's came with the production numbers printed on the dials. The 1950's model Timex watches are all very obvious by their styles and type of movements and frequently have the year of manufacture stamped in ink inside the back. The earliest models from the 1950's have "Made in USA" printed at the 6 o'clock position.
By the way, if you happen to have access to a digital camera and could either email or post some photos, that might be helpful in matching your watch with a photo from a vintage Timex sales catalog. If you're able to take photos please also take one of the movement inside your watch.