1880's Elgin Giant Railroad pocket watch

This 20 year rolled gold pocket watch belonged to my great grandfather who was born in 1875 and I think it was his father's originally. I just inherited it and had no idea of value so I took it to a jeweler who specializes in estate watches. He gave me an appraisal of 1000.00 +. He said it was an Elgin railroad watch even though the face says"Illinois Watch Co." Inside the case the numbers are 53089 and the numbers all match in 3 places. Inside the case it says Elgin Giant. The serial number on the movement is 289457 and it says Illinois Watch Co.,Springfield, Ill.It runs and keeps decent time. The case is decorative but has no engraving. I think the crystal covering the face may be plastic. My mom had it replaced a few years ago and it doesn't sound like glass when you plink it. Also with a magnifying glass I can see what looks like a tiny hair on the face. Not sure what that is. I will consider any reasonable offer. offers. I will try to answer all questions but I know very little more than what I have said here.