I own a S&W 455 Mark II hand ejector second model, made for the british army. It was later rebored to 45 Colt. It has the usual british stampings - and e six-digit serial number. But only 74000 were made. The serial Number is 2039xx. It is stamped under barrel and under the frame of the grip. When you open the cylinder you can see a "6510" stamped on the frame opposite the hand of the cylinder. Do you know, why the serial-number is so high?