Eberhard & Co Age determination by year of manufacture Chronographs

With the years of manufacture/calibers of chronographs below, you may be able to roughly estimate the age of an Eberhard&Co watch:

1920 push-button chronograph, hand-wound, white dial, yellow gold

1935 Chronograph extra Fort, cal. 110, hand-wound, gold-plated metal

1936 Valjoux Cal. 65, 17 jewels, hand-wound, red gold-plated

1938 first "Eberhard&Co Chronograph, hand-wound, gold-plated movement, gold dial

1938 Chronograph Valjoux Cal 65, 18K with hinged case, white dial

1940 Valjoux Cal. 65, two-pusher chronograph, 18K, tachymeter scale, 2 sub-dials

1945 Chronograph Valjoux 72, 18K, 17 jewels, 3 subdials

1950 Extra Fort Chronograph, hand-wound, yellow gold, silver dial

1960 Valjoux 7768, stainless steel, moon phase, limited to 989 pieces

1987 Caliber 14, Sterling silver case, 21 jewels, limited to 4000 pieces

1989 Valjoux Cal. 7751, chrome-plated metal, full calendar/moon phase, limited to 999 pieces

1990 Valjoux Cal. 7751, gold-plated, automatic, full calendar, moon phase

1990 Lemania caliber 872, 17 jewels, gold-plated stainless steel

1997 "8 Days", mechanical, hand-wound, silver dial, stainless steel

Source: Wolfgang Salm "Wristwatches", Wikipedia