Selling Blackberry Tour, I have a question

I have a new blackberry tour that I want to sell. My question is, this phone is supposed to be unlocked and there isn't any carrier branding on it. Is there any way of telling if this is in fact unlocked? I just want to make sure that if I sell it it will work with other carriers. I am not very familiar with blackberry's and came into this one by pretty much luck but I don't need it.

Thanks, Graham

This isn't an eligible market place posting nor is this the marketplace forums. Please refrain from posting any sort of sale offers for it.

The easiest way to tell would be to slide a SIM card in the device and see if you can get signal, their are other ways but this would be best for someone with no BB knowledge.