This was made in 1897. Tsar Nicolas II presented it as a gift to his wife Tsarina Alexandra, on the day of their coronation in the Uspensky Cathedral in Moscow on 26th May 1897.
The egg is made of gold, with an unusual translucent yellow guilloché enamel covering it. Diamonds criss-cross it, with black enamel double-headed eagles at the crossing points. (The Tsarina wore a gold robe to the coronation, and the double-headed eagle was the Imperial symbol of the Russian empire).
Inside the egg was a minature diamond and enamel replica of the 18th century carriage in which the Tsarina arrived to the Coronation. The windows of the coach are made of rock crystal and the wheels are made of platinum. The wheels move and the doors open - it's a functioning jewelled toy.