I think I should add to the information about the meter. This meter is a depression meter. Meaning, it was introduced after the 33/37/38 ECO models, why, it was the depression, meters were not selling, so ECO decided to bring out a very stripped down meter. This meter originally sold for $33.50. It is very overlooked piece of mid-30s petro history (only because it is so plain looking).
Author, 1st & 2nd editions of Gas Pump ID book, 3rd edition is now available at www.gaspumpbible.com
Air Meter ID book also available