Here is my contribution to this thread:

S/N: S18890x Four Screw

According to its letter: "Shipped from the factory on March 30, 1959 and delivered to Union Hardware & Metal Co., Los Angeles, CA. Shipped with 6 inch barrel, brush blue finish, and checkered walnut grips. Records indicate that this order was for 10 units in this configuration. Target grips were added after being originally shipped from the factory."

Any thoughts on this 10-revolver order, the hardware store, or what agency in CA might have used this revolver would be greatly appreciated.

Thanks