Duplicate Keys

That's good information. Please excuse my lack of knowledge, but my car came with one key that has a button that I was under the understanding controlled the door locks. the button does not work and a new battery in there didn't seem to help. Supposedly there's a little light in there too, and the light doesn't work with a new battery so I just assume the Chip/circuit was bad. I was hoping to get a replacement for that

The Porsche 928 was never delivered with door lock-unlock via key button.  All the button does is turn on the little lamp in the key ... so in the dark you can find where to insert the key.

Some 928s today may have that feature, but only as an aftermarket installation.