There is no true definition of what constitutes oil rubbed bronze. Most agree, in broad terms that Oil Rubbed Bronze should have darker brown tones with a bit of the metal base material showing through.
How you get there is another story, and often you can not get there at all. Many are happy to give the illusion of oil rubbed bronze by faux-finishing the piece or using a spray paint of some sort. This makes it very difficult to have a little metal showing through, since we are talking paint in this case. Look at oil rubbed bronze furniture, lamps, and kitchen and bath accessories. You will usually find that the coloration is very uniform and consistent. The reason for this is two-fold, One, many of us seem to desire uniformity in our furnishings. The manufacturers give us that by basically painting the items or dunking metal plated items in a chemical tank. Easy, cheap, and uniform, and just what we want, Right? Oh, and very profitable for this "premium" finish.
If the look of aged real metal is desired you will have to accept that aging and patina are not uniform and will differ from item to item. There can be extreme beauty in the variability associated with metal and the aging process. You can see the variations by looking at the statues and buildings in any older city. Beautiful! But certainly not cookie-cutter!
Here is how the craftsman creates the oil rubbed bronze look. Beginning with metal, or a finish comprised of real metal, chemicals are applied that alter the metal and change the color. Think of patina as rust, and rust as patina. But what we call rust is only common to ferrous metals such as iron and steel. Other metals naturally patina in their own way and show wide differences of color depending on such variables as salt air, pollution, and temperature. Brown tones as well as greens, blacks, and blue often show on Bronze, Brass, and Copper.
The skilled patinator works her magic to produce these natural colors without waiting a couple of centuries for the patina to develop. Chemicals in various combinations are applied to give the desired look. Greens, blues and browns each require different techniques, but the final step is the same. To give the natural look, the highlights are hand rubbed letting the beauty, luster, and life of the underlying metal to peek through.