Sarah Bush Johnston photograph

[Steve]

I was wondering if anybody had any information on the history of the more well-known Sarah Bush Johnston photograph. I have a link to the image of it here, so you know which photo I'm talking about:

https://www.lincolncollection.org/discov...item=37250

I know it's a copy of an apparently lost original. If I remember correctly, it was a member of the Johnston family who brought the photo to public attention. Does anybody know which Johnston that was? Also, have there been any attempts to date the image based on clothing, etc; or try and make educated guesses as to what kind of photograph the original was; or try and figure out approximately when the copy was made?