Solid brass casting with an attractive polished and lacquered finish and a stepped edge as a border, BUT when the button is pressed to ring the bell, the metal of the switch button and the casting also becomes connected to the bell's electrical circuit.
The face plate measures 74mm by 32mm and is 5mm thick. The 'wired switch' with its pair of screw terminals needs an 18mm diameter hole at least 15mm deep behind the back of the face plate.
The switch assembly needs to be fitted into the face plate, and this is difficult to do without damaging the lacquer finish, fortunately I have some ultra-clear lacquer
spray for finishing paintwork or artwork and this served to repair the scratch and add a couple of extra sealing coats to improve the wear and weather resistance.
I docked two stars because of the potential Electrical Safety issue with the button not being properly isolated from the wiring. If there is a problem with the low-voltage bell transformer (all too possible with the prevalence of non-CE-approved cheap direct imports from the far East) then this could present a significant Safety Hazard. There is a Duty of Care requirement here.
Previously with another supplier's switch using the same style of contacts I needed to take apart the switch and slightly loosen the rivet holding the copper contact disc on the button press, this tiny bit of extra float allowed a much easier contact when pushing the button. But that copper disc quickly oxidised in just a few weeks, maybe it was not up to the bell current.
In my final application with this new bell push I have discarded the nylon plug carrying the contacts and am actually just using the sprung button to push a plastic rod to operate the switch of a wireless bell hidden behind the mounting surface, so for me neither the possibility of random contacts nor the lack of insulation are any longer a concern.
Addendum. 27th June 2015
It seems that many wired door bell switches use this same unsafe configuration. They have the same two terminals in a nylon bung screwed into the brass/chrome body, and the push button completes the circuit AND connects the pressing finger as well. This is not a problem if the transformer is properly Class III (Double Insulated with Safety Extra Low Voltage, eg 6V or 12V AC), and the circuit is genuinely fully floating at zero potential with respect to ground. However if the Double Insulation is not up to standard (I've measured and rejected several unsafe non-CE transformers) then there is the possibility of the bell circuit carrying a substantial fraction of the mains as a floating voltage; this is potentially lethal.
The easy route to safety is for the switch body and button to also be insulated from the circuit.