It's deffinately a 60s.
I have this knowledge because I spend far too much time reading 1960s magazines and building websites on the girlfriends/wives of The Beatles. So what with working out which outfits the girls wore to which event, and reading magazines full of "what's in this season" I usually find it quite easy to pin things down to a certain section of the 60s.
It's fabulous to find a useful outlet for all of this here. Usually I irritate friends and family by complaining all the way through any modern film or TV programme set in the 1960s.
<li>"There's no way you'd wear a 1967 dollybird outfit with a 1962 housewife's hairstyle and 1950s shoes!"</li>
<li>"That didn't come out until 1972 so why are they wearing it in 1965?! And that eye-shadow colour didn't come out until three years later, what are the researchers thinking of?!"</li>
...unfortunately I also complain about the wallpaper and the furniture, so you can see what I drive people mad! LOL!
Anyway, this dress has caught me out, so I'm intrigued. I'll be keeping an eye out for this sort of style now in my magazines.
And I do really love it here because I'm learning so much more, getting an endless supply of fabulous pictures of 60s outfits to try and "guess the year", and everyone is so lovely!

...I'm also spending a lot too. LOL!
love, moons and starrs,
Senti.*