OK, I looked at the front sight under magnification and found the drift pin through the polished bluing and the repair to the rear of the sight band.  Removed the band and found a flat milled into the top of the barrel under the band.  Possible Carbine barrel that did not have a front sight soldered on?

Regardless, to install a M1903 front sight band will need a woodruff key on the flat to keep the band from rotating. Believe a 1903A3 band and key can be installed but would not look like the correct "vintage".  An A3 key fits under the 1903 band with the milled flat but the drift pin clearance is in the wrong place and would require cutting the key or drilling a new clearance notch. Anyone else tried to replace a front sight and have a key solution?