David Akers (1975/88):
The 1854-O has virtually the same mintage as the 1853-O and 1854 but it is more common, all grades considered, than either of them. However, almost all known 1854-O Eagles are well worn with VF the predominant grade. In high grade, AU or uncirculated, the 1854-O is extremely rare and I have not personally seen a mint state piece.
The 1854-O comes with both small and large dates. The latter is much the rarer of the two and is seldom available in any condition. The difference in date size is great (unlike the 1842 for example where the difference is rather small).