70 odd years to Princess Sibylla of Sweden photographed with a young King Carl Gustaf (her youngest child and only son) in a fantastic calot/beret with feathers.
Images from Getty as indicated
Royal Hats
The Bold, Beautiful and Bizarre World of Royal Millinery
Royal Hats 
I love this hat! It looks as though it could be worn today, perhaps by Max.
I agree it’s a lovely hat. What really gets me is that Sybilla looks a bit more like his Grandmother than his Mum – not because she looks particularly old (she was 40ish then), but because women of all ages dressed and styled their hair in similar ways.
I’m just reading the Norman Hartnell biog (really good!) and I’ve got to the early 60s where he’s got the third generation of the same family coming to him for frocks! Of course that largely changed in the subsequent decade, but it’s interesting to ponder.