This Colt Police Positive Special Revolver was shipped to the H & D Folsom Arms Company in New York, New York on July 23rd, 1927. It was on the Colt Factory Order #13235 / 100 in a 5 gun shipment. The factory letter calls for a blue finish with Checkered Wood Stocks.
While this is a Police Positive, it's commonly referred to as a Pre-Detective Special. They are unique with their short and stubby barrels, along with no model name, or patent information stamped on it.