It is a particularly rare Western bitters bottle, which would make it extremely collectible and of significant value, because antique western bottles tend to be more in-demand than equivalent Eastern bottles, and bitters bottles in general are one of the most prized "types" of bottles to collect. I can't guess at its value, but if you listed it properly on eBay I'd expect a 4-figure return. Any more details about the discovery that you'd like to share?