Ooh - lot's of responses. Thanks everyone!
As far as the eye spacing is concerned, I still think it may be the same woman, and they just look closer together due to parallax. I did some measurements on the photographs, and if they are the same person, for the eyes to look that close, the head would have to rotated about 30 degrees with respect to the straight-on photograph. I think this could be true for the unknown photo.
This rotation could also account for the slightly different jaw line and cheek shape, since it's fairly difficult to get an impression of the 3-dimensional facial structure from only the straight-on photo. I also measured the ratio of the vertical distance between the eyes and nose and eyes and mouth, and it was essentially identical for the two photos - 0.6, though I'm not sure how much this varies between different people.
The woman actually died in September, 1886, the same year the photo was taken, at the age of 51. She was not Amish as far as I know. Being farmers in rural Vermont, I doubt they had much need or means to own very fancy clothes.
If the photo was cropped by the scanner, it only cut off a few pixels. I think the photo itself might have been cut to fit in the album. I do have another photo that would appear to be contemporary which was not cut down as much, which I'll post here. I actually was curious about whether this is the same woman as another photo I have too. I can post it here, or start another thread for it.
