The first thing most collectors do is to look at the serial number of a Thompson that is shown to them. This is a good way to immediately identify the age of the gun. The serial number of this Thompson is A0-104570. this would normally mean a gun built in W.W.II by Auto-Ordnance, Bridgeport. However, upon looking at the right side of the receiver you will notice that it is actually a West Hurley. How could this happen?

Simple. During West Hurley’s production of 1928’s customers could order a Thompson with a "customized" serial number. Why this number was picked is anyone’s guess. But this should prove that you should examine all sides of a gun.