This is used in eject assembly in the pinball playfield.I do not have access to an original, so it is possible that some dimensions are not exactly the same as the original.
If you are interested in pinball and 3d printed parts, have a look on my new blog: http://3dwingmaster.blogspot.com/ describing my quest for a pinball using most parts made with a 3d printer.
For a smooth inside surface, use a small layer height. e.g. 0.15 mm.Fill 40% .. 100%