Bought this at a garage sale and don't know anything about it

I bought this desk at a garage sale and seller says it came from a well to do family in Michigan. She said that the family owned a railroad and home burnt down and this was saved. Has been in her family since the late 1800's. Only mark found was in the mirror and only showed up when I happened by it with my flashlight. Would love to know more about it and value.Attachment 7933Attachment 7934

I know it made from Mahogany.