When talking about Apple prototypes, you sometimes come across terms like EVT, DVT, or PVT. Here’s a brief explanation based on the information I’ve found (feel free to correct me if I’m wrong).
EVT stands for Engineering Verification Test. The goal is to verify that it actually works functionally. EVT models may differ from the final models in certain aspects if there are any bugs. For example, the Spartacus prototype on eBay illustrates this point.
DVT stands for Developer Verification Test. In this case, the focus is on verifying that the software functions correctly. For instance, the iPod touch 3G with a camera is an example. These prototypes seem to be the most common ones circulating, from what I’ve observed.
Finally, PVT stands for Production Verification Test, essentially an identical device to the final version used for testing before it goes on sale. For example, the PowerBook G3 prototype is an instance of a PVT.