I think this is a hard one, and one would maybe have to handle it and get a feeling for it. I first though 30s too, but it does look incredibly "new". But stranger things have happened...
I have several late 1930s German magazines here that have lots of sewing, knitting and embroidery patterns. There are a few peasant-style blouses and dresses with embroidery in there, but the embroidery motifs are all in one color (red on white) and more geometric and mostly in cross stitch, save one dress with a corn flower-embroidery and a drindl dress with broad floral embroidery on the skirt and around the neck. The blouses all don't have a neck opening like this blouse here, with the slit and the ties - the 1930s blouses just have a small round neck opening.
I have also seen loads and loads of 60s/70s embroidered peasant blouses in secondhand shops in Vienna, and have been wondering if maybe these were also produced in eastern Europe at the time - like Hungary or Czechoslovakia. Things from there always made their way to Vienna - I see that with other things too.
@Pauline - how interesting to hear! I couldn't say that this embroidery looks especially Swiss, but things like this were certainly produced in Switzerland too. I have just acquired almost the complete year 1946 (just one issue missing) of a weekly Swiss sewing/handicraft magazine. This was a time of patriotism and traditionalism, and there are lots of embroidery things in there too, but I haven't yet had time to look through every issue. So far I haven't found seen anything similar regarding the embroidery. I will probably blog them, as it's so much to take in, and I've already seen so many interesting, funny and weird things in there that are worth sharing! Who knows what more I'll find.
Karin