How old is my watch! Wakmann/Gigandet Age determination based on models with known years of manufacture

No documents of serial numbers with year of manufacture can be researched from Wakmann / Gigandet

Here is a list of chronographs with a known year of manufacture for age determination "not older than ...":

1949 Chrono 18K Cal Venus 170, hand-wound, 2 sub-dials

1950 Chronograph Cal Landeron 248, 18K, rhodium-plated, hand-wound, push-button case back

1952 Chronograph Cal. Venus 188, hand-wound, white, 2 sub-dials

1960 Chronograph INCABLOC, silver, 2 sub-dials, nickel-plated, decorated, manual winding

1962 Chrono full calendar Cal Valjoux 730, hand-wound, 3 sub-dials

1965 Chronograph "Olympic Games" Cal Valjoux 7733, screw back, 2 auxiliary digits.

1965 Chrono full calendar Valjoux 723, column wheel, hand-wound, 3 sub-dials

1965 Chrono full calendar Valjoux 726, gold-plated, column wheel, 3 auxiliary dials, hand-wound

1965 Chrono Valjoux 7730, black/white, chrome-plated, hand-wound, 2 sub-dials

1966 Chrono "Plaquee d`Or", Cal. Valjoux 730, hand-wound, full calendar, bar indices

1967 Chrono full calendar Cal Valjoux 730, blue-white, 3 sub-dials

1968 Chrono Cal Valjoux 7730, hard chrome-plated, hand-wound, INCABLOC, hand-wound

1969 Chrono rotating bezel, Landeron 51, hand-wound, INCABLOC, 2 auxiliary dials.

1070 Chrono full calendar Valjoux 730, column wheel, day/date, manual winding. 3 subdials.

1970 Chrono Cal Valjoux 7734, hand-wound, bar indices + sub-dials

1972 Chrono Automatic Cal. Lemania 1341, Day/Date, Gold/Colored, Tachymeter

Source: Classic Wristwatches catalogue, Wolfgang Salm "Wristwatches"

1975 Chronograph full calendar Cal Valjoux 730, column wheel, screw case, 3 sub-dials

1975 Chronograph cosigned "Breitling" Valjoux 236, column wheel, rhodium-plated, gold, 2 auxiliary dials.

1975 Full calendar automatic, Lemania LWO 1341, regatta scale, dec. 12h counter, date

1975 Chronograph INCABLOC Cal Valjoux 726, rhodium-plated, column wheel, 3 sub-dials