The Radar Sentry enjoys it's prestigious place in history as (for all practical purposes), the first commercial radar detector! A LOT more history and data on the Radar Sentry can be found on the Radar Sentry on our page about The First Commercial Radar Detectors.
This particular Radar Sentry is probably the oldest detector in the whole Radar Detector Museum! This unit was certainly manufactured before June 18, 1963 when the patent was granted, and possibly even before Radatron officially applied for a patent on the unit on August 3rd, 1962! There are a couple of things that make this particular Radar Sentry unique. This unit does not have the extra plastic antenna on the back, as later "patent pending" units do. Also, this unit includes the extra metal bracket for holding the clip on, which is absent on later "patent pending" units. In the Popular Electronics article from 1961, both the lack of antenna and presence of the extra bracket can be seen, suggesting that this unit might be from around 1961-1962 .
Note the "patent pending" at the bottom of the face.
Notice the lack of the plastic antenna on the back, also no patent number.
This radar sentry has the extra metal bracket:
Later "patent pending" units do not have this bracket.
Fron the 1961 Popular Electronics article.