Hi there, what you have is a circa late 1950's-early 1960's machine made bottle. The OI on the base is an Owens-Illinois Glass Company mark, and that particular mark they used from the mid-1950's up until the 1960's. Not sure what it contained without a label, but my best guess would be a chemical or cleaning solution, as the wide threading on the lip looks like it would fit a measuring cap. It vaguely has the shape of a whiskey flask but it is lacking a "Federal law forbids sale or reuse of this bottle" embossed lettering required on all alcoholic beverage contains up until 1964, so I doubt it contained alcohol UNLESS it was manufactured in the mid-1960's. Hope this helps!