Just so the is no mistake the 1857 overly map is a hybrid map created from an existing 1851 map. The overlays were done using "LIBERTY" in the crwon for the obverse and "ONE CENT" for the reverse.
I don't collect these, or know much about them, but the first thing I spotted was that date. It just doesn't look right to me.
I would buy it for $50 for further study in hand and under a microscope. Corrosion is very deceptive and may make a worn coin look like a cast copy. Just my opinion. It does have characteristics of a genuine coin but also of characteristics of a transfer die struck piece. Further study needed but I would opinion a worn genuine coin.