Has decreased in popularity, Hamlin is a much more common early-season orange
Description from The Citrus Industry Vol. 1 (1967):
" Fruit medium-large, globose; base with short, radial furrows; areole indistinct; moderately seedy. Well-colored under favorable conditions. Rind medium-thick; surface finely pitted and moderately pebbled. Flesh color dull orange; firm, juicy; well-flavored. Very early in maturity, possibly the earliest.
Tree vigorous, large, and productive. Its outstanding earliness soon popularized this variety and it quickly became the leading early orange, a position held until about 1920. Parson still remains a major variety in Florida, however, though it has never achieved prominence elsewhere, principally because of seediness. "