This is the Colt marked 'U.S.'.  As is expected with US Colts of this vintage, the serial numbers do not all match.  The Colts were regularly sent back to the factory for new parts and repairs due to regular government use.  The serial numbers on this gun are 13,587 / 7021 / 37,764.  The gun is beautiful. 

The U.S. stamp is very clear, on the left side of the frame, to the right of the patent dates. 

For Ordnance Department purposes, the frame serial number is considered to be the number of record for the gun. The under-barrel cartouche, "RAC", is that of Rinaldo A. Carr, a sub-inspector who worked under the supervision of Lt. Horney between 1890 and 1903.  The 'P' signifies that it was refurbished during that time, confirming that this gun was sent back to the Colt factory for the repairs that caused parts to be added that were stamped with differing serial numbers.  This is a straight factory gun, not a parts gun.

As is correct for a Colt of this very early time period, there is no rampant colt stamp, nor is there a 45 COLT stamped into the barrel.  The mother-of-pearl grips on this Colt are pristine.  Neither grips have a Rampant Colt button in them.  The grips were changed to the mother-of-pearl Colt grips by Capt. Davis to make them more 'parade worthy'.

The button on the ejector rod is a ring, as is appropriate to this model.  The action is smooth and tight.  There is a normal wear line on the cylinder from rotation during use.  According to his daughter, they were not fired by her father during the time that he owned them.

The factory stamp along the top line of the barrel reads:

COLTS PT.F.A.MRG.Co.HARTFORD CT.U.S.A.