[rackops]

Here's the gas gauge diagram out of the judging standards. The JS reads:

The early 1928 gas gauge had a vertical oval opening
with a flat lens and was used through May 1928.
In April 1928 the gas gauge was redesigned from
a nickel-plated steel casting to an aluminum die
casting, nickel-plated on the exposed face. Nickel
plating was not used after June 1928. The aluminum
frame gauges had a magnifying glass lens with a
horizontal oval opening through mid-1929. In May
1929 a round gas gauge opening was introduced.
Initially, the round glass had a flat raised center.
This was changed to flat glass by November 1929.
The gas gauge face plate was satin black with a
horizontal white nickel line across the center. Some
vehicles in mid-1931 to the end of production had
a gold line. The line was 1/32" wide from the
beginning of production through May 1929 and
3/64" wide thereafter. The numerals on the gauge
quadrant were black, except in early 1928 when the
"0" and "F" were brick red and slightly larger than
the other figures.

Gas gauges were secured into the gas tank with a
nickel-plated brass outer nut. Initially, the nut was
7/16" thick with a conical pocket. In January 1928,
the thickness was increased to 15/32" and the inside
edge was rounded with a 1 /32" radius. In February
1928, the pocket was changed from a conical pocket
to a pocket with a radius (see photo).