In 1965 Citizen launched a major line of watches called the ‘Crystal Seven’. which has to do with the type of glass used, it’s the first time Citizen used ‘crystal’ – possibly equal to Seiko’s ‘Hardlex’ mineral glass or something harder. The ‘Seven’ continued Citizen’s use of this title first seen a year earlier, in 1964, in both auto-dater and hand-winding models.
Using automatic non hacking movements (the 52xx series) with oscillating weights rather than the circular geared rotors as seen in earlier ‘Jets’, it was Citizen’s main automatic line of watches at that time, but there are no Crystal Sevens in the 1971 catalog and onward.
As on many 60’s Citizen casebacks a lot of cryptic symboils and text can be written. In no particular order, for this type of Crystal Seven watch only:
Star - Refers to Citizen’s watch case divison. A summary history of the Citizen Watch Companuy states: “1932 Citizen merges with the watch case factory Star Shokai.” This company was originally set up in Japan to import Swiss Mido watches. Even before that time, in the early 1900s, there was a history of cases being made in Japan into which Swiss movements were fitted.
Para water: Citizen watches were increasingly marked ‘Parawater’ after 1958 when Citizen designed water proof cases for the first time. ‘Parawater’ continued until the early 1970s when it was replaced by ‘Water Resistant’.
Three letter codes: usually this is the Case Material Code – often this is an abbreviation, and is usually self-explanatory as in CGP (Citizen Gold Plate).
This watch however has GN2. GN simply means it is a Crystal Seven watch and the 2 should refer to the second generation which would place it in the late sixties.