William Mooty's head stone measures 12" wide, 4" thick, and 1 5/16" from the tip of the top down to the height of the side. (I held a straight edge from the sides where the taper starts, and measured from the tip to the top of the straight edge.)
Mary Mooty's head stone measures 12 11/16 wide, 4 " thick, and 1 1/2" from the tip of the top down, using the same method as above.
So between 1911 and 1923 there was a difference, as you stated it is not noticeable unless you actually measure it.
We do not have any idea what year her stone was placed, but maybe since you have the measurements this will tell us a little more about the stones and maybe where they came from, and even a range of years of when they were placed.
Thanks again for all your help, I am really getting anxious about what all we are going to find about this couple.
tom