Antique Mandolin

This mandolin belonged to either my grandfather or my great grandfather.  There is no manufacturer label on it.  On the bottom of the footplate it says Pat'd Oct 6 86, which would have to mean 1886.  One screw is missing for a string, one string is broken, and one string is missing.  The wood is in excellent shape.  I am interested in obtaining an approximate value, but not for sale. Also any information about who could have possibly manufactured it.  Thank you.