Now that's interesting! Often, a Colt 1878 was stripped of its barrel and this served as a donor barrel for a Colt Single Action Army revolver, since the barrels are interchangeable.
Since the SAA revolver is the more desirable of the two, this makes sense.
Now, the barrel on this Colt 1878 contains an italic barrel address, which means it originated from a Colt SAA revolver, serial number ~22,000 or under. Far more valuable on a Colt SAA than on a Colt 1878/1902. Hence, a rather curious finding.