identify the model can be detected to distinguish between are non-ferrous metals or ferrous metals

Detection Range:≥23cm(for a RMB noe Yuan coin or for a US quarter)    Signal Frequency:7.2KHz   Audio Frequency:413Hz   Power Supply:DC9V(6*1.5V AA batteries)    Connection Rod Length:1.1M  This instrument with high accuracy rating,it's with the recognition mode with non-ferrous metals and ferrous metal identification.It's used to archaeology,search metals that hidden in udnerground