Dave wrote:

At one time I believe the PTO actually required the
inventor to send it a working model. No more. I believe the inventor must
persuade the examiner that if the device were produced in accordance with
the specifications it would do what the inventor claims it would.


I believe that is correct Dave. BTW what do you think of the idea of patenting a drug for treating a specific disease and then later on finding
another disease to treat with the same drug, and as result being able to extend the original patent?

Cheers
Marty