Hi, just recently a fantastic Heuer timepiece came across my way. It is a 36mm diamater case, 2 dial chrono. Dial is black with arabic main indexes plus 60 sec.scale at edge of dial. Case material is steel for the back and case body seems to be brass covered by a nickel film. Movement is a Valjoux 22. Case no. inside of back reads 42531. Can somebody help to identify age plus ref. no. ???