As you will see in this video above, apparently Verizon's version of the iPhone 5 is actually unlocked and can even take a GSM nan-SIM right away. Here's a quote with some of the details,
Please keep one thing in mind... this only applies to legitimate nano-SIMs, so make sure you are careful before trying this out. The cut-and-stuff hack jobs will not "cut it."Aside from handling Verizon's LTE waves just fine, the nano-SIM slot will also accept cards from any other GSM carrier worldwide. In other words, AT&T nano-SIMs will get you onto its HSPA+ network, and T-Mobile nano-SIMs will play nice as well. If you're heading overseas, you can pick up a local nano-SIM on arrival and plug it straight in -- no unlocking code necessary. To confirm, this even applies to Verizon iPhone 5 units that were purchased under contract.