Sorry to add confusion but I would say Body Shape would be the best way to tell them apart if your hen does not have a rose comb.
Because many RIW now have single combs, mine do.
Stromberg's sell RIW with a single comb http://www.strombergschickens.com/prod_detail_list/Best-Egg-Laying-Chickens
The Rhode Island White is a single comb,
So does E-Fowl - single comb
http://www.efowl.com/Rhode_Island_White_Chickens_p/2017.htm
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Traits: The Rose combed variation was the only variation of Rhode Island Whites to be admitted to the standard originally;
however, the 2010 Standard of Perfection now discusses the Rhode Island Whites with Single combs which is now the most common variation. Their combs, face, wattles and earlobes should be bright red, their eyes reddish-brown, and their beak and legs yellow.
Good picture of the single comb RIW
http://www.dare2dreamfarms.com/#!rhode-island-whites/c1ypx
The breed continued to be developed and improved so that it more closely resembled the Rhode Island Red’s
brick-like body shape. This distinctive shape
helped to prevent the breed from looking similar to and being confused with White Wyandottes or White Plymouth Rock chickens. The Rhode Island White is a moderately-sized, completely white bird with the males weighing 8 1/2 lbs. and females 6 1/2 lbs.
They have
long, broad, and deep bodies which are carried horizontally, giving them an oblong and brick-like appearance overall. Their breasts are deep, full, and well rounded. Their heads are fairly deep and are inclined to be flat on top rather than round.
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Definition: Rare Heritage Breed RIW
Breed Description:
Legs & Beak: Yellow
Comb: Straight or Rose
Earlobes: Oblong, well defined, smooth, & red
And for the White Rocks we see :
White Plymouth Rock Chickens
White Plymouth Rock Chickens or
White Rock Chickens are one of the most popular variations of the
Plymouth Rock chicken breed along with the
Barred Plymouth Rock and have been extremely popular in America since their introduction in 1869. Originally
Plymouth Rocks were bred as a dual-purpose fowl, valued both for their meat and the hens' egg-laying abilities.
The ongoing and growing popularity of these chickens with the “backyard chicken” movement is largely due to it's docile and easily tamable nature, tendency to brood , long life expectancy, and excellent production of both eggs and meat. Families wishing to raise chickens at home as pets will find these friendly birds as an excellent choice.
White Plymouth Rocks are relatively large chickens. The face of the
Plymouth Rock is red with red ear lobes, a bright yellow beak, bay-colored eyes, and a single comb of moderate size. Their feathers are fairly loosely held but do not easily tangle. The comb of this breed has five evenly serrated points with those in the front and rear shorter than those in the middle.
White Plymouth Rock Chickens lay large eggs that vary in color from light to medium brown, sometimes with a touch of pink. The birds continue laying all through the winter with decreased production. On average, each
Plymouth Rock hen will lay around 200 eggs per year.
Product Facts
White Plymouth Rock Chicken Info
- Adult Weight - Male: 9.5 pounds ; Female: 6 pounds
- Color - White, Yellow Skin, Smaller Red Comb, Red Face and Earlobes