Gracias a todos por vuestras respuestas. Con vuestra información y mediante la intercesión de San Google he podido encontrar más unidades parecidas a ésta, la principal diferencia entre todas ellas es la corona, en ninguna coincide.
Buscando y rebuscando he encontrado informacion sobre calibres Longines que incluyo más abajo. Seguro que para muchos es redundante, pero no obstante la pongo por si a alguien le sirve de ayuda.
Definitivamente lo voy a traer a casa, creo que se llevará bastante bien con mi Omega Seamaster vintage y así podran recordar viejos tiempos.
Estimated Longines production dates
<table border="0" cellpadding="0" cellspacing="0" width="585"><tbody><tr> <td bgcolor="#c0c0c0" width="10" height="26">
</td> <td bgcolor="#c0c0c0" width="49" height="25"> Date
</td> <td bgcolor="#c0c0c0" width="91" height="25"> Serial
</td> <td bgcolor="#c0c0c0" width="49" height="25"> Date
</td> <td bgcolor="#c0c0c0" width="91" height="25"> Serial
</td> <td bgcolor="#c0c0c0" width="49" height="25"> Date
</td> <td bgcolor="#c0c0c0" width="93" height="25"> Serial
</td> <td bgcolor="#c0c0c0" width="49" height="25"> Date
</td> <td bgcolor="#c0c0c0" width="108" height="25"> Serial
</td> </tr> <tr> <td width="10">
</td> <td width="49" height="20"> 1867
</td> <td align="right" width="91" height="20"> 1
</td> <td width="49" height="20"> 1905
</td> <td width="91" height="20"> 1,750,000
</td> <td width="49" height="20"> 1922
</td> <td width="93" height="20"> 4,000,000
</td> <td width="49" height="20"> 1946
</td> <td align="right" width="108" height="20"> 6,500,000
</td> </tr> <tr> <td width="10">
</td> <td width="49" height="20"> 1870
</td> <td align="right" width="91" height="20"> 20,000
</td> <td width="49" height="20"> 1907
</td> <td width="91" height="20"> 2,000,000
</td> <td width="49" height="20"> 1925
</td> <td width="93" height="20"> 4,250,000
</td> <td width="49" height="20"> 1947
</td> <td align="right" width="108" height="20"> 7,000,000
</td> </tr> <tr> <td width="10">
</td> <td width="49" height="20"> 1875
</td> <td align="right" width="91" height="20"> 100,000
</td> <td width="49" height="20"> 1909
</td> <td width="91" height="20"> 2,250,000
</td> <td width="49" height="20"> 1926
</td> <td width="93" height="20"> 4,500,000
</td> <td width="49" height="20"> 1952
</td> <td align="right" width="108" height="20"> 8,250,000
</td> </tr> <tr> <td width="10">
</td> <td width="49" height="20"> 1882
</td> <td align="right" width="91" height="20"> 250,000
</td> <td width="49" height="20"> 1911
</td> <td width="91" height="20"> 2,500,000
</td> <td width="49" height="20"> 1928
</td> <td width="93" height="20"> 4,750,000
</td> <td width="49" height="20"> 1953
</td> <td align="right" width="108" height="20"> 9,000,000
</td> </tr> <tr> <td width="10">
</td> <td width="49" height="20"> 1888
</td> <td align="right" width="91" height="20"> 500,000
</td> <td width="49" height="20"> 1912
</td> <td width="91" height="20"> 2,750,000
</td> <td width="49" height="20"> 1929
</td> <td width="93" height="20"> 5,000,000
</td> <td width="49" height="20"> 1956
</td> <td align="right" width="108" height="20"> 10,000,000
</td> </tr> <tr> <td width="10">
</td> <td width="49" height="20"> 1893
</td> <td align="right" width="91" height="20"> 750,000
</td> <td width="49" height="20"> 1913
</td> <td width="91" height="20"> 3,000,000
</td> <td width="49" height="20"> 1934
</td> <td width="93" height="20"> 5,250,000
</td> <td width="49" height="20"> 1959
</td> <td align="right" width="108" height="20"> 11,000,000
</td> </tr> <tr> <td width="10">
</td> <td width="49" height="20"> 1899
</td> <td align="right" width="91" height="20"> 1,000,000
</td> <td width="49" height="20"> 1915
</td> <td width="91" height="20"> 3,250,000
</td> <td width="49" height="20"> 1937
</td> <td width="93" height="20"> 5,500,000
</td> <td width="49" height="20"> 1962
</td> <td align="right" width="108" height="20"> 12,000,000
</td> </tr> <tr> <td width="10">
</td> <td width="49" height="20"> 1901
</td> <td align="right" width="91" height="20"> 1,250,000</td> <td width="49" height="20"> 1917
</td> <td width="91" height="20"> 3,500,000
</td> <td width="49" height="20"> 1938
</td> <td width="93" height="20"> 5,750,000
</td> <td width="49" height="20"> 1966
</td> <td align="right" width="108" height="20"> 13,000,000
</td> </tr> <tr> <td width="10">
</td> <td width="49" height="20"> 1904
</td> <td align="right" width="91" height="20"> 1,500,000
</td> <td width="49" height="20"> 1919
</td> <td width="91" height="20"> 3,750,000
</td> <td width="49" height="20"> 1940
</td> <td width="93" height="20"> 6,000,000
</td> <td width="49" height="20"> 1967
</td> <td align="right" width="108" height="20"> 14,000,000
</td> </tr> <tr> <td width="10">
</td> <td width="49" height="20">
</td> <td width="91" height="20">
</td> <td width="49" height="20">
</td> <td width="91" height="20">
</td> <td width="49" height="20"> 1942
</td> <td width="93" height="20"> 6,250,000
</td> <td width="49" height="20"> 1969
</td> <td align="right" width="108" height="20"> 15,000,000
</td></tr></tbody></table>