Datasheet Page 67: Identification register

Dear all,
what is this register used for ?

Thank you

It is a register that always returns a word composed of high byte 0x53 and low byte 0x00 that is the type number of chip (0x5300 = W5300)
I understand that the brother W5500 has an identical register at 0x0039 location (that returns 0x55 0x00) and the W5200 at 0x001F location.
Since each chip has a different location find it of little use except to verify the correct reading of a known value register.