This is an egg shaped container with screw thread. Ideal for sweets and toys - not just on easter.

Printing

If you are using PrusaSlicer - pre-configured slicer projects are included in the download.

If you start from STL:

The bottom part of the container can be printed standing as designed without supports. 

The top should also be printed as designed standing on its bottom edge. It may require a brim, since the edge is very thin. The PrusaSlicer project adds a thin support tower in the middle to prevent sagging of the top.

The decorative shroud can be printed upright or reversed. It definitely needs a brim.

FreeCAD

The FreeCAD 1.0 design file is included in case you want to modify it.

The base shape is a “Moss's Egg” (as described on Wikipedia). It is split at the widest point using a boolean operation.