During the 1970s and early 1990s, Vivitar serial numbers took the following form:
MM Y WW SSS
MM = manufacturer code
Y = year; may be ambiguous, for instance 1979 and 1989
WW = week
SSS = item-specific serial number
The manufacturer codes used by Vivitar are:
09 - (or 9) Cosina Company, Ltd.
13 - Schneider Kreuznach
22 - Kino Precision
25 - Ozone Optical Co., Ltd.
28 - Komine Co., Ltd.
32 - Makina Optical Co., Ltd
33 - Asanuma & Co., Ltd
37 - Tokina Optical Company, Ltd
42 - Bauer (possibly Bauer trademark holder Robert Bosch GmbH)
44 - Perkin-Elmer
47 - Chinon Industries, Inc.
51 - Tokyo Trading (possibly a corruption of Tokyo Koki, a Tokina predecessor)
56 - Kyoei Shoji Company, Ltd.
61 - Samyang Optics Co., Ltd
75 - Hoya Corporation
77 - Kobori Mfg Co. Ltd
81 - Polar
Of these, a few appear to be highly regarded, such as Kino/Kiron (22) and Komine (28). Others have become household names, such as Tokina (37) and Samyang (61).