Bronze is non-ferrous; it is not attracted by a magnet. Bronze is reddish when polished. It corrodes to a colour in the range pale green to dark brown.
Bronze is an alloy of 90% copper, 6% tin and 4% zinc.
The difficulty with identifying bronze is that a bronze effect has often been achieved with a plated or lacquered finish. 'Spelter bronze' and 'French Bronze' were popular from the 1850s to the early 1900s. Similar finishes are also common on door furniture from the period between 1930 and 1960. Paint or varnish, with bronze pigments, was applied to cast iron. These painted finishes may develop copper oxidation. Alternatively a very thin copper plating was applied to a metal surface. A third method was a coloured lacquer. Do not attempt to polish any of these finishes.
Like brass, bronze is used for door and window furniture although it is more rare.
Heating a metal containing zinc can cause zinc oxide fumes or dust. Exposure can cause irritation of the eyes, nose, and throat and a flu-like illness called metal fume fever.
Should you clean tarnished bronze? As in the case of brass, the normal practice would have been to keep it shiny. However, there are some risks to cleaning bronze. Firstly, you will tend to lose an attractive patina that is itself a protective layer. Secondly, if the metal proves to have been plate or a bronze-effect paint or lacquer, you will destroy the finish.
Painted bronze can be stripped with standard chemical stripper.