Here is one from the same shipment and letters the same. It has the standard width grip frame like the Navy models do and is marked USN but the letter shows USMC. These 85 guns look like all of the other Navy 1909's in design but serialize in the lower range of the USMC revolvers which serialized in from 23,101-26,300 range with many gaps in their production. I would assume that these 85 revolvers saw use with the Navy as the Marine production used a special order smaller grip frame. Since the Marine production superseded the Navy production we would assume that some of the gaps in production serial numbers were used to produce these 85 revolvers. One can also assume that these 85 were sent to the Navy Department ahead of the regular production run. The standard USN production was in the 52,000-53,000 range and the Navy contract was for 1000 revolvers. The butt markings included the USN with an anchor and the caliber marking .45 and then numbered 1 thru 1000.
This is a 1909 Navy from the standard time production period:
This is a 1909 USMC with the narrow grip frame for comparison. The butt markings included the USMC and the markings from 1 thru 1300. These were all purchased through the Navy Department beginning in May of 1909.