longines serial numbers
1870=20,000 1871=36,000 1872=52,000 1873=68,000 1874=84,000
1875=100,000 1876=121,425 1877=142,850 1878=164,275 1879=185,700 1880=207,125
1881=228,550 1882=250,000 1883=291,670 1884=333,340 1885=375,010 1886=416,680
1887=458,350 1888=500,000 1889=550,000 1890=600,000 1891=650,000 1892=700,000
1893=750,000 1894=791,100 1895=832,766 1896=874,432 1897=916,098 1898=957,764
1899=999,430 1900=1,124,715 1901=1,250,000 1902=2,083,333 1903=2,916,666 1904=1,500,000
1905=1,750,000 1906=1,850,000 1907=1,950,000 1908=2,100,000 1909=2,250,000 1910=2,375,000
1911=2,500,000 1912=2,750,000 1913=2,900,000 1914=3,075,000 1915=3,250,000 1916=3,375,000
1917=3,500,000 1918=3,625,000 1919=3,750,000 1920=3,815,217 1921=3,880,434 1922=3,945,651
1923=4,047,100 1924=4,148,549 1922=3,945,651 1923=4,047,100 1924=4,148,549 1925=4,250,000
1926=4,500,000 1927=4,625,000 1928=4,750,000 1929=4,886,360 1930=4,959,088 1931=5,031,816
1932=5,104,544 1933=5,177,272 1934=5,250,000 1935=5,333,330 1936=5,416,660 1937=5,500,000
1938=5,750,000 1939=5,850,000 1940=5,950,000 1941=6,140,900 1942=6,331,800 1943=6,522,700
1944=6,713,600 1945=6,904,500 1946=7,106,750 1947=7,309,000 1948=7,511,250 1949=7,713,500
1950=7,915,750 1951=8,225,535 1952=8,535,320 1953=8,845,105 1954=9,183,125 1955=9,521,145
1956=9,859,165 1957=10,201,415 1958=10,543,665 1959=10,885,915 1960=11,211,988 1961=11,538,061
1962=11,864,134 1963=12,368,962 1965=12,621,376 1966=12,873,790 1967=13,839,112 1968=14,834,158
Esto te dará una aproximación, si es un Longines, por lo que preguntas.