That is a very nice Monogram, especially with the second set of barrels. He doesn't give the serial number and gives a date of 1903. There are records of guns having the HOT before 1904, but most of them will not have the serial number of the gun on them. Also without a letter it is hard to say if the second set of barrels came with the gun from the factory.
Unusual to see the gold inlaid "lighting" at the breech, they usually had scroll there and at the muzzle. The A3 and Deluxe models had that, but you could have whatever you wanted, within reason.
In my opinion a great aid in selling this gun would be a letter or not.
Letter or not, whether gun came with second set of barrels from the factory, it is still a great piece of American workmanship. There were only 131 made from 1893-1918, and 140 between 1918 and 1945, 2 were made in a .410