You can date your 1930's car from the codes etched into the Triplex glass for more complete information see this page
In the Triplex trademark the words TRIPLEX and TOUGHENED were arranged in a circular formation around a triangular arrangement of the three X's. Glasses were defined by the quarter of the year (Jan - Mar, Apr - Jun, etc.) and the year of manufacture.
The quarters were depicted by a dot above the word TRIPLEX. (The 4 quarters corresponded to the first 4 letters of TRIPLEX. T=1, R=2, I=3, P=4). The year was indicated by a dot under one of the letters of the word TOUGHENED (9 letters for nine years T=1931, O=1932, etc). For 1930 the dot would be placed to the right of the letter D
if the etching looks like this then it indicates that the glass was made in the second quarter of 1934