OK, I found a medal identified by Mark Parker in 2003.I don't know how to provide a link to that page. I googled "medal gratia dei servatus" and scrolled down to find it. He says it was issued by Sons of Union Veterans (VS).And the date he gave is 1881.That is the correct date on your medal.He put the value at $20.Thing is,the photo he shows is the back of the medal.