PRECIOUS METAL TESTING MAGNET
Extra large earth magnets are used on Fine jewellery that are gold or silver plated where ferrous metals are used as the base metal. If a magnet responds to jewellery, it is not fine silver or anything near pure gold. Same for brass and bronze antiques, many are just brass plating over a steel or iron core. 
Keep this magnet in your pocket and test items quickly, 
The magnet can also be used to determine polished aluminium from stainless steel in most cases.
50MM X 40MM X 10MM