It can be hard to tell, the Rhode Island Reds tend to be more brilliantly colored and slightly larger (but that's not always so). You can also wait. A production red will only lay for two years and will look all used up (dull feathers and very little meat). A Rhode Island red bull late up to four years (I even got five from one hen). A production red chicken will lay one, possibly two, eggs per day and a Rhode Island red chicken will only give you 3 to 5 eggs a week. I discovered this news by accident when I was shipped production reds instead of Rhode Island's one time.