Hi, I read some time back that THE MODEL 1851 COLT NAVY was only made in the 36 bore only and not 44 bore, the 44 bore revolvers that are out there were not made by Colt. Unless the forum members knows different.
For in-depth reference on Colt Model 1851 London Navies see ‘Colonel Colt, London’ by Joseph G. Rosa, ‘51 Colt Navies’ by Nathan L. Swayze or ‘The Book of Colt Firearms- 3rd Edition’ by R.L. Wilson. For values, check out ‘Flayderman’s Guide to Antique American Firearms and their values’ by Norm Flayderman