The WPD is a typical police department marking. When you see PD think Police Department. SO means Sheriff's Office and HP is often Highway Patrol. Many agencies stamped such an ID and inventory number on their guns. I have one stamped FHP for Florida Highway Patrol and another marked CCPD for Corpus Christi Police Department. Some folks collect police guns while others don't appreciate the extra markings.

Yours was used by some city PD and the city name started with W.

__________________
No life story has happy end.