Thanks to all who sent responses. It appears that this field is indeed a
site-specific customization. The confusion is that each of the three people
who do such things here is pretty sure that he did not add the field, so
they were convinced that it came with some update to the package. Guess not.
Although they're also pretty sure that the field affects the operation of
the product, so it may be one of the optional fields that is conditionally
processed by the code. The APPDIC field number is 3546.

Steve