How sure are you about the exact wording of the inscription? A very common form of wording on a stone would be "In loving memory of...." for the first name, then "Also of" followed by another name, and in this case that would be a logical arrangement.
"of" and "at" might be confused on a quick reading, or if the lettering was in an unusual font. Erosion can play a part too, though it might be less of a factor with a stone of that age.
Can you tell us where the stone is, and whose names are on it? Someone might have access to an alternative transcription, or even a photo (unless you have one that you could post).