The model number indicates that it was a specially built gun rather than a standard one. Is there any engraving on it? Or it may have simply had different sights, etc. than normal back then. The description means it was built specifically for the West Memphis Police Department. Odds are it was a trade-in gun when they got rid of their 96Ds in favor of whatever they bought next.
It has a WMPD marking followed by a 4 digit number on the opposite of the dust cover from the serial number. It also has night sights, which I assume are factory.
The engraving alone would make it a "Special" in the Beretta-speak of the time.