Ok, I searched a bit further, and went on Google Finland (google.fi) - I admit, my curiosity has been piqued! Helsinki is one of my favourite cities, and Finnish design simply is some of the best. Anyway, I found a few more vintage fashion blogs in Finnish, that show Merry Finn dresses, all probably 60s.
http://pupulihavisto.blogspot.com/2008/07/maalaiselm-pilvimekko-ja-toinenkin.html
The red dress with black belt.
http://emmin.helmiblogit.mtv3.fi/2009/06/
First picture - short red dress.
http://annikainenpuikoissa.blogspot.com
The black and copper dress
And here's a vintage clothes online shop:
The green dress on the left on the second last row on the bottom.
And here's a book from 1980, by the Finnish Foreign Trade Association, that mentions Merry Finn too, alongside with icons like Arabia, Marimekko, Artek Fiskars, Aarikka etc., so the company must have still been operational then:
http://www.huuto.net/fi/showitem.php3?itemid=117590406
My knowledge of Finnish is very basic, so I can't say much more about what it says there. :spin:
So there's a lot of variety around, and I think we can say they were at least around from somewhere in the 60s to 1980.
And I must say, there are some really pretty dresses by them! I must look around for that label when I go to Helsinki again, and visit one or the other shop that has vintage fashion.
Karin