You have a classic Dutch onion bottle. Believe it or not, it dates to the early 18th century.
Much of the glass from the 17th and 18th centuries was what we call "black glass" or glass that is dark olive green in color. Glass of this color became known for its durability.
Your particular bottle appears to be more of a medium or emerald-ish green. One does see these bottles in this color but much less frequently.
Your bottle is also what many would call "sea washed" in that it spent a good amount of time on the ocean floor.
Chris has it right. This is a classic Low Country onion from say 1720 - 1740. Many thousands of these bottles were produced over a long period in the 1700s. The condition of this onion reduces its collector value to $50 - $100, I'd say. In good condition with original gloss, it might bring $150. It all depends on your market, of course.
Comments
You have a classic Dutch onion bottle. Believe it or not, it dates to the early 18th century.
Much of the glass from the 17th and 18th centuries was what we call "black glass" or glass that is dark olive green in color. Glass of this color became known for its durability.
Your particular bottle appears to be more of a medium or emerald-ish green. One does see these bottles in this color but much less frequently.
Your bottle is also what many would call "sea washed" in that it spent a good amount of time on the ocean floor.