233P3H1V0 is an unnamed c/3 orthogonal spaceship discovered by Hartmut Holzwart in April 1994. It is notable, because it was the first non-monotonicperiod3 spaceship to be discovered.[1] Since then some smaller non-monotonic c/3 spaceships have been found based on the same front end.
Image gallery
A 151-cell non-monotonic c/3 spaceship based on 233P3H1V0 RLE:here
References
↑David Bell's archive of c/3 ships and puffers in Life