Colt 1851 Navy Small Guard Conversion serial # XX820. All matching original numbers. (No renumbering done as is the case on many conversions.) Note the unusual features. 1) No ejector system 2) Unusual loading gate and opening device 3) No gap at rear of cylinder between conversion ring and cylinder. Conversion ring fits flush with frame rather than over lapping 4) Rimfire firing pin is long and tapering conical (possibly needle fire). The only example in Bruce McDowells book on Colt conversions is an experimental needle fire from the Connecticut State Library, see page 380. This gun has 93-94% blue on barrel. Cylinder scene is mint. Grips are excellent quality of the work is excellent. Neat conversion.