Whether it's 1950s or 1960s - I'm not fussy, it's lovely.
As long as it's M series (late 1950s/early 1960) or N series (mid to late 1960s) it's the cat's whiskers.
I have a hunch it might be 1958 as Augusto says, for one reason, if you look at the feet of the accordion - see how they are smoothly integrated into the accordion bass casing - that's a feature of the M series. However, it would be nice to know more about the other variations in the design...
That said, I like pretty much all Scandalli's.
The brand new Scandalli Super VI Extreme is lovely, oh and the Scandalli Air VI is awesome... not to mention the Scandalli Intense.