Narcissa Prentiss Whitman Picture Button with mirrored back

I was going to College in Walla Walla, Washington in 1978 and living off campus in a very old colonial style home that was basically turned into a "frat house."  Myself and a couple of friends agreed to rent the house with the agreement that we would clean it up and paint etc...

While cleaning I found a box of stuff that was labled "garbage" and looked inside and saw a lot of old pictures, newspapers, and this item that, even almost 40 years old, looked like an antique. When I saw the name I recalled the "Whitman Massacre" and the history of what had happened in that area in the 1800's, so I kept the button and NOW wish I would have kept the whole box.  Anyhow...that is the story of how I came in possession of it.  It was tossed in my jewelery box and has been there ever since until I rediscovered it while moving into my new place.  I thought it might be found of interest to someone out there.  I would love to know anything I can about it because it is definitely a piece of Washington/American history.