Any idea?

The sapphire necklace tiara


https://www.instagram.com/p/DIgpCoSCbmV/

Indeed, it is the sapphire tiara made from the former necklace of Queen Emma's sapphire parure:




By the way, the tiara seems to be worn a bit akwardly, leaning to the Princess' left...

I didn’t know that branch of the family attended state events like this visit?

Prince Jaime has been the Dutch ambassador to the Holy See he has held other positions within the department of Foreign Affairs. It seems he also has had something to do with Oman. The only other banquet he and his wife attended was in Rome during the Dutch State Visit to Italy. This is her third tiara after the ears of wheat at their wedding, the lower part of the antique pearl or pavlovnik pearl tiara in Rome and this in Amsterdam.

Interesting to see she didn't curtsey to the King or Queen.

Perhaps a curtsey was done before in private?

Really a shame that there are no jewels left in the ducal house of Bourbon Parma

It was Queen Juliana who abolished curtsying at the Dutch court early in her reign. So Viktoria did precisely what was expected of her. She kissed her cousins on the cheek and a handshake and nod for the Sultan.

I actually thought Queen Beatrix reinstated it.

No Beatrix returned to being adressed as Your Majesty instead of mevrouw (madame). She did not reinstate curtseys or court dress abolished under her mother. Around 1969 Queen Juliana stopped the use of most court uniforms for the men in her household. Queen Beatrix did alter the way the Royal Household is run and restored all three of the main palaces: the Royal Palace in Amsterdam, Noordeinde Palace and Huis ten Bosch Palace both in The Hague. Juliana has the reputation of being simpler but if you look at state events Juliana was way more glittering than Beatrix ever opted to be.

Jaime is a senior civil servant and as far as I know, still the Dutch Climate Envoy. He might have had some involvement in the (preparation of the) program for the Omani delegation because I can't see why else he would attend the state banquet to be frank. Viktoria is involved in international agri-food policy development, which might also have a link to Oman or the visiting program. Whatever the background it is unusual to see them here. It seems Constantijn and Laurentien are mainly invited when close (family) royal friends are visiting. Margriet and Pieter only join sporadically these days. A pity. A broader representation of the RF looks so much better. Amalia is making up for it these days but has less conversational topics I suspect,