1890 Durand Mirror

I bought an antique mirror off of Craigslist and I am curious as to its value. The mirror has a large bevel and a solid wooden back that was nailed on. I popped the back off to see a marker that read "Durand & Po.." (I couldn't make out what was after the Po- at least I think it was Po,it was smudged) and "Patent Silvering Process" below it. The words had a circle of stars around them and "June 13 90" below it.