That's actually a three part mold, it had 2 side halves and the base 'cup'.
The United Drug Company didn't start until 1903, so the first decade of the 20th century
would be my estimate for your bottle. As I mentioned it has that familiar Rexall shape.
These are often found with the metal crown stoppers.
from Surf's earlier post...
"In 1902, Louis K. Liggett persuaded 40 druggists to invest in a drug company that would manufacture and distribute products in franchised stores. In 1903, the United Drug Company (UDC) began operations at 43 Leon Street, now known Meserve Hall at Northeastern University. The stores and products were known by the name "Rexall," for "king of all." By 1929, UDC had 21 manufacturing plants throughout the United States. It employed over 25,000 workers, supplied 10,000 Rexall Drug Stores, and operated a chain of over 500 Liggett Drug Stores in the United States. In 1944, Liggett stepped down. Justin Dart, the new president, renamed UDC the Rexall Drug Co. and moved the headquarters to Los Angeles. In the 1930s, UDC built six buildings on its Boston campus that housed its corporate offices and manufacturing and research facilities. Northeastern University purchased the buildings from United Realty in 1961.