Thanks for posting Elsie
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.
