This Colt Bankers Special Revolver was shipped February 1931 in a 650 gun shipment. The letter reads Factory Engraved: "RMS No. 9804" as is seen on the butt and the backstrap of the revolver.
The Railway Mail Service was a sub-unit of the United States Post Office. At the time the RMS was the biggest transporter of domestic mail by volume. They operated out of rail cars, sorting the mail en-route and exchanging mail at stations without coming to a complete stop.
RMS clerks often transported large sums of money, including acting as escort to federal gold shipments. This made robbery a real and present danger, requiring the armament of the clerks. While a large number of armed clerks rode the rails, most of the issued revolvers were reportedly destroyed at the end of their service lives.
This pistol does bear the inspector mark "GWA" on the left side trigger guard. It is believed that this is the inspection mark of Col. George A. Woody who was believed to be stationed at Springfield Armory during this time period.