Crown is a period 12 oscillator that was found by Noam Elkies in January 1995. Alternatively, it may refer just to the 10-cell piece at the top of the oscillator in generation 10 (shown below in green) that is hassled by two caterers and a heavyweight emulator.
It is used in the pi orbital and p156 Hans Leo hassler.
A 52-glider synthesis is known for a variant of this oscillator which uses two jams rather than two caterers for stabilization.
By replacing the caterers with extensible p3 oscillator, an extensible crown can be made:
Generation 10 reveals a piece that by itself is sometimes referred to as the crown