There are some small tests you can do where you may be able to identify whether an item is authentic brass or not. Brass is a non ferrous metal. This means that it is not magnetic so a magnet will not stick to it. Conversely if the magnet is attracted to the metal then the item is most definitely not brass. You could also scratch the surface of the 'brass' and check what the color is; if the color revealed is a silvery color then it is likely a white metal with a brass plate coating.
- Hang on, what if it IS brass, won't I ruin it by scratching it?
- How much would that cost me?
- Ouch! Would it be cheaper to get it done professionally?
It may well be, although prices are difficult to assess given the wide array of shapes and sizes that can be electroplated. Below are a couple of websites that can give an estimate on the cost
Brass Metal Plating
Spectrum Metal Finishing
Brass Metal Plating
Spectrum Metal Finishing