There is absolutely no question in my mind that your flask is an authentic 19th century piece. Any knowledgeable collector would look at the photo of the base and come to the same conclusion.
There are a number of different molds for the original Railroad flasks. I am aware of at least two or three different reproduction molds which are slightly different that the originals. There is one mold believed to be from the early 20th c. that might fool some novice collectors - the others have a modern glass weight and feel.
