How to know, is the handset was unlocked?

Sim-lock, SP-lock, “coding” - all these words have similar meaning: a programmed limit in the phone to work with a single network. A sim lock allows a network provider to prevent handsets from being used on other GSM networks. Usually those handsets are sold with a discount, and the provider covers the price difference. The handset stays inside the same network and within a year pays back the expenses of the service provider.

Know By the external attributes:
- if there is a logo of the network provider on the front panel;
- if there is a foreign to the manufacturer language sticker underneath of the battery;
- visible traces of disassembling of the new handset;
Phone's menu has a brand of some network provider (Orange, T-Mobile, Vodafone, Cingular, ATandT etc… )
And the last one is a low price.