Queen Silvia at Queen Beatrix's 60th birthday celebrations

For Queen Beatrix of the Netherlands' 60th birthday celebrations, Sarah found that Queen Silvia for Nina Ricci on both nights. 

The celebrations took place on January 30 and 31, 1998, in Amsterdam. Those in attendance included Prince Alexander (the Prince of Orange), Prince Charles, King Harald and Queen Sonja of Norway, Queen Margrethe and Prince Henrik of Denmark, King Constantine and Queen Anne-Marie of Greece, King Juan Carlos and Queen Sofia of Spain, and Grand Duke Henri and Grand Duchess Maria Teresa of Luxembourg.

On January 30, the festivities were held at the Muziek Theater where the Dutch Royal Family and other royal guests enjoyed a ballet performance where Silvia wore the glittering, snakeskin gown while carrying a matching silver clutch. Her gown was not revealed until she had gotten inside the theater due to the cold temperatures; she kept warm in her fur coat.

On the evening of January 31, guests were treated to a gala dinner at the Royal Palace of Amsterdam. This palace is the working palace and not one where the then Queen of the Netherlands lived. 

Queen Silvia wore a purple Nina Ricci gown with diamond floral earrings. Her shoes were matching the gown, and Her Majesty kept warm in a long fur coat. 

On both occasions, King Carl XVI Gustaf was in black tie.

This snakeskin gown she still wears to this day.