Colt 1862
Here is one of the rarest if not the rarest Colt Revolver ever made.
It is the Model 1862 3" Octagonal Barrel Pocket Navy Conversion.
On Page 340 -341 of his book, A STUDY OF COLT CONVERSIONS by R. Bruce McDowell, he describes this little rare gun and says he knows of but nine. This one is # 21062 which is just 3 #'s off of one he lists. I have seen a couple of more so I would say there were as few as 12 ever produced.