Be careful of your customers' choice for the door hardware finish, especially if your customer chooses a BHMA category B finish, 613, 640, or 704 which are like US10B, the nearest former U.S. Equivalent. A category B finish is not stable, the final color varies depending upon the hardware's base material, the manufacturer's processing methods, etc. Visible finish variations can occur if the door hardware purchased is from different manufacturing lots.
Oil Rubbed Bronze BHMA 613/US10B base metal is bronze. The finish is produced by oxidizing the hardware in a special solution, which is then heated to a temperature that produces the desired appearance. Then a mixture of oil and wax is applied. This final product is an applied finish.
Over time, weather and people handling the lock will cause a change because the rubbed finish has no protective coating or plating. Usually, the visible change to the finish is where it is contacted by peoples hands. The contact and the chemicals in peoples hands, rubs away the finish and exposes the base metal. Areas untouched will continue to oxidize and darken.
However, the US10B finish is available with ANSI 640 Oxidized Satin Bronze Plated steel and ANSI 704 Oxidized Satin Bronze plated (oil rubbed) zinc. When the visible change occurs under contact with peoples' hands, the base metals are different, further increasing your customers' dissatisfaction.
With all of the new stable finishes available, where possible avoid the category B finishes.