Just to fill in a few points.
In addition to the sizes of the pumps listed by Jim, there was also a 15 gallon visible pump.
The first visible pump appeared around 1916-1917, pumps before then look similiar to the salesman sample shown above.
Visible pump, besides being hand operated (used mostly in areas where they had no electricity), they were also made to be operated by electric motors or air operated, or any combination of the three.
Most of the questions you ask are answered in the "History of the Gas Pump" section of my book. Some of the questions would require a great deal of research to answer them.
Jack Sim
Author, Gas Pump Identification book and Air Meter Identification book

Author, 1st & 2nd editions of Gas Pump ID book, 3rd edition is now available at www.gaspumpbible.com
Air Meter ID book also available