No third lock, no shroud. SN 44519 left side of Barrel "Smith & Wesson .455." period in front and following the numerals. Right side of barrel, no markings. Not many british markings. Crossed pennants left frontside of frame, small logo right side of frame. Only a couple of small stamps, one right side over front of trigger guard. One on left side over the stock medallion too vague to see, over II. Two line adress top of barrel, crossed pennants rear of cylinder. Hope this adds to your data.

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dd884
JMHO-YMMV