Ernst-Jan Beeuwkes wool dress and jacket dating and info on designer?

I had a quick look at the Dutch Wikipedia entry for him

Code:

https://nl.wikipedia.org/wiki/Ernst_Jan_Beeuwkes

. From what I understand, he started by making had for several years for a boutique called Marie Louise, which was at Noordeinde 26 in Den Haag (The Hague) and which had been founded in 1926 by a Louise Preller.
To that I might add that that's a pretty prestigious address in The Hague. Whilst Amsterdam is the capital of the Netherlands, The Hague is the seat of government and where the King or Queen has the official residence - Paleis Noordeinde, so that's the same street. Even today that address has some of the more prestigious/expensive shops in The Hague (I have been there numerous times and I love it ).
Anyway, he worked for the boutique making hats for 5 years. He left in 1956 and launched his first own hat collection that year. From 1959 he started selling his own creations as well as creations from Paris and Milan. In 1975 he stopped doing couture himself and, if I got that right, went on to just sell clothes by other brands/designers. Many of his creations are now in the collection of the Gemeentemuseum in The Hague, which is an important design museum. The shop continued after his death in 1998, and was finally closed by the new owner in 2007.

I would date your pretty ensemble to about early 60s, but let's see what the others think.