The Blaupunkt Frankfurt US was certainly the most common radio installed in U.S. '02's. This is a monaural unit. Other Blaupunkt models, especially the Frankfurt Stereo US, were also commonly employed. Intending no slight to other brands of radios installed in U.S. '02's -- Becker, Motorola, Grundig, etc. -- here's a summary of how to date and identify Blaupunkt radios of the era. This is borrowed from a thread commenced on September 3, 2013, entitled "Dating 2002-Era Blaupunkt Radios".
Above is a stock photo of a 1969 model Frankfurt US (Model 7639 670), used in the U.S. 1974 2002 brochure!
I've noticed interest lately, on behalf of some forum members, in using period-appropriate Blaupunkt radios. This comes after decades of removing radios installed by the original dealers in order to install more modern, and generally better-sounding, radios and stereo systems. What goes around, comes around. I personally am also curious about being able to date 2002-era Blaupunkts that lack their original paper labels. Examining examples of Blaupunkt radios with labels enable us to do this.
Let's first descibe the Blaupunkt system for labelling radios of this era. A self-adhered paper label, generally placed on the right side of the unit, identified it by model name, model number, serial number, and country of manufacture (first photo below). Let's look at the details.
Beginning, it would appear, in 1967, the 4th digit of the model number signified the model year of the radio ("model year" as contrasted to "year of manufacture"). Thus:
7637 XXX = 1967
7638 XXX = 1968
7639 XXX = 1969
7630 XXX = 1970
7631 XXX = 1971
7632 XXX = 1972
7633 XXX = 1973
7634 XXX = 1974
7635 XXX = 1975
7636 XXX = 1976
Note: the "763" numbers immediately above are illustrative; not all model numbers begin "763." And not every model, e.g., Frankfurt, was available as a new or "refreshed" model each year. New models were often introduced two or three years apart.
Moving on from the model year, a letter prefix for the serial number -- in a manner similar to that for Becker radios -- denotes the year of manufacture. By the dawn of the '02 era, 1966, Blaupunkt was nearing the end of an alphabetical series:
X = 1966
Y = 1967
Z = 1968
So they started over in 1969:
A or B = 1969
B = 1970
C = 1971
D = 1972
E = 1973
F = 1974
G = 1975
H = 1976
J = 1977
K = 1978
Therefore, labelled Blaupunkts are easy to date. And labelled 1967-and-later radios actually bear two date indicators: first for the model year; second for the year of manufacture. And as is apparent below from two 1969 model Frankfurt US units, and from two 1975 model Frankfurt Stereo US kits, a model may have been manufactured well beyond its model year.
The second and third photos below show two stacked Frankfurt US units. The top, unlabelled unit, is a 1971 model Frankfurt US (763"1" 627 000, based upon an identically-labelled unit shown by JohnH elsewhere in this thread). The bottom is a 1969 model Frankfurt US (763"9" 670), manufactured in 1971 ("C" prefix to the serial number). But if you return to the first photo below, you'll see another 1969 model Frankfurt US (763"9" 670). But that example was manufactured in 1970 ("B" prefix to the serial number). The fourth and fifth photos below show two stacked 1975 model Frankfurt Stereo US Kits (763"5" 421 012). The top unit was manufactured in 1975 ("G" prefix to the serial number) and the bottom unit was manufactured in 1976 ("H" prefix to the serial number).
The last two photos below, i.e., the sixth and seventh, show probably the last German-manufactured U.S.-spec radio of the '02 era, a 1976 model Frankfurt Stereo US Kit (763"6" 421 012). This example was manufactured in 1978 ("K" prefix to the serial number), and I've not yet seen an example manufactured in 1976, but I'm confident a few are out there.
Many facets of the faceplates and pushbuttons changed over time. The blue dot or point (as in "blau punkt") appeared and later moved during this period. The "Blaupunkt" name shifted locations. The number of station numbers represented, along with the actual choice of station numbers, transitioned over time. "Stereo" changed from vertical to horizontal.
Pushbuttons moved from black with white letters to black with silver and black applied labels. And then they came up with the clunky "combined" AM/FM buttons of the 1976 model. The FM scale went from a reverse orientation -- higher numbers on the left, lower numbers on the right -- to a more expected low-to-high orientation. (FM scales that end at 104 rather than 108 signify European versions: the European countries use a slightly narrower FM range.) The spacing of the scales' call numbers changed. And there were more changes, no doubt, such as to the size of the housings.
Feel free to add photos of Blaupunkts, along with their identification labels, below.
Thanks and regards,