This is the My Little Pony: Keepsake Musical Jewellery Box. The box features the ponies (but no Twilight Sparkle, or Applejack though) on it. And for some reason, Fluttershy is now an earth-pony. Inside, there is a miniature Pinkie Pie that spins around when the jewellery box music plays.
Here is the other side of this jewellery box: [link]
My Little Pony: (c) Hasbro. Created by Bonnie Zacherle. G4 characters are designed by Lauren Faust. Jewellery Box is by Hunter Leisure.