Well after using Google I found in the archive section of this site that 104 is a prefix for the 150 5V Autostrada. But no mention of date. Further Googling would put it down to around 1969. You could try the German Gilera site, plenty of owners of the older bikes on there.
thanks, your right, it`s not as i thought (and as it is badged) a giubileo sport extra, but as you say an autostrada 150v, and probably 1969, don`t know who did the original dating certificate .....anyway, i don`t mind , i like it,