This was made in 1895. Tsar Nicholas II had just got married. It was a tradition in the Imperial Family for the Tsar to present a jewelled egg to his wife, and to his mother, for Easter.
The Rosebud Egg is what Nicholas ordered for his new wife the Empress Alexandra, to symbolise love.
It has cupid's arrows made of diamonds on the bottom half. The egg itself is made of gold which is covered with translucent red guilloché enamel. The rosebud is made of enamel.
There were other surprises in the egg (which are lost now, and we only know of them through old photographs) - a tiny diamond-set crown and a ruby drop.
Here's a copy of an old photo of it. The miniature crown is in the Russian style: