I wondered about the missing tabulator settings and key, but I found this link about a first edition Valentine, also Made in Italy and also missing the tabulator set/clear and key.
And the mystery about the serial number is solved — Stephen Green from the Facebook Olivetti Valentine group suggested that the hyphen might actually be a 4, so I cleaned it up some more and took another picture and, yes, the number is 3000408. Since the first Valentine was the 3000001, this is one of the first Valentines.