What is Nokia 5310 PUK Code?

The PUK-code is (Personal Unblocking Key). It is NOT unique for Nokia Phones. If a user enters the wrong PIN-code 3 times in a row, the telephone asks for the PUK-code as is supplied by the network operator for that telephone. Don't lose it! If the PUK-code is wrongly entered 10 times in a row the SIM-card gets locked up permanently.