The 1934 A twenty-dollar bill from San Francisco with the serial number L40736387A is a rare and valuable note. According to the book _United States Paper Money Errors_, by Fred Reed and Neil Shafer, this note is known as the "double eagle error" because it was misprinted with the same serial number twice. Only four notes of this type are known to exist, making each one extremely valuable.
The value of this note can vary depending on its condition and where it is sold. In general, it can be worth anywhere from $10,000 to $100,000 or more. However, it is important to have the note authenticated by a professional before selling it to ensure that it is genuine.