First, don't listen to anyone who doesn't own one of these damn things.
Locksmith, serial numbers, forget about it. I did it already so you can learn from my visit to Senor Locksmith here and save your money!
JR has the right idea, read my write up about it and you will understand the workings of it.
The fix is very simple when you understand how it works.
Take a look at the area of the locking cap that sits flush with the hole. That part can be grasped with a pair of pliers and you simply turn it and it will come out.
If you still have difficulty, send me a PM and I will help you.
As for anyone else contemplating the purchase of this item, think long and hard before wasting your money.
I doubt I would even sell mine to someone used.