The 1839-O Large O Rev of 39 has an "O" mintmark where the inside left of the "O" is aligned directly below the oustside left column or leg of the "M" in "DIME" and the "O" mintmark is perfectly centered on the reverse with no tilt or rotation whatsoever away from 12:00 o'clock reverse. The much rarer 1839-O Huge O Rev of 38 has an "O" mintmark where the absoute center inside the "O" aligns directly below the center of the left column or leg of the "M" in "DIME" and the O mintmark has a slight tilt to the right away from 12:00 o'clock reverse. The 1839-O Huge O Rev of 38 also shows the "O" mintmark much closer to and almost touching the right knot of the ribbon whereas 1839-O Large O Rev of 39 has a much more obvious distance away from the right knot. (Stock #10c1839503 Large O Rev 39 SORPAKG SYRGfUZW)