A side issue of potential interest:
Dating your car by its windows - based on the original compiled by Neil Cairns.
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     "MG's made in the 1950's to the late 1970's can be dated by the 'TRIPLEX CODE' etched into the toughened glass. My 75 GT has Sicursive side glass but a Triplex heated back-light with a code that fits the date of build of the car. This also works for any other make using TRIPLEX glass. Note that it dates the GLASS, so is only an indication of the cars age, assuming the glass is original. If you are not quite sure of the year of your car, but the decade is known, just look for two dots in the TRIPLEX logo on the glass.

One dot above T, R, E, or X gives the quarter of the year the glass was manufactured:
     T = Jan, Feb, March,
     R = April, May, June,
     E = July Aug, Sept,
     X = Oct, Nov, Dec.
But which year?
Nine letters make the word TOUGHENED,
one dot below a letter gives the year of the decade:
     T = 1
     O = 2
     U = 3 and so on.
     However, if you see no dot, the year is zero.
     Say your car is a 1950's MG, then
     TRIPLEX TOUGHENED, with one dot over the 'R' in Triplex, and the other under the last 'E' in Toughened, indicates 'April/May/June 1958'

Below are some date code pictures. The first (from previous page) is a 1950's vintage logo. The other four were supplied by Kevin McCabe on June 9, 2006: Per note at top of page, the dots above the letters T, R, E and X would represent 1st through 4th quarter of a production year. The triple-X logo is obviously older issue compared to others. The "TP" or "LP" designation may refer to Triple Plate or Laminated Plate, being composed of two layers of glass with the plastic film in between to prevent break-up of the glass if it is smashed. The term "Toughened" may refer to hardened and tempered safety glass, which is the type that breaks into a million pieces smaller then your fingernail if it is smashed. I believe the tempered glass is a newer contrivance which can be stronger and may be manufactured in thinner plate to be less expensive. Post war items are easily recognisable as from 1945 onwards the BS logo (or “kite mark”) was added below the original TRIPLEX logo.

This brings my attention to the year code. Word of warning here. The last four pictures came from a 1969 Rolls Royce, and the word "SUNDYM" is apparently a trade name for tinted glass. Notice in the first picture above the word AGREE with dots over the 4th and 5th letters. This may be 5+4=9 for the 9th year of the decade (origin of this picture is unknown). The next two pictures have "SUNDYM" with dots under the 2nd and 6th letters, which may be 6+2=8 for the 8th year of a decade. The next picture has "SUNDYM" with dots over the 3rd and 6th letters, which may be 6+3=9 for the 9th year of the decade. These three pictures can make sense for original glass in a 1969 model car.

The last picture shows the later style logo with the word "toughened" with a dot under the 5th letter which would be the 5th year of the decade. This might be a later production replacement glass for the same car.

Now notice the first three pictures have a dot in the center of the triple-x logo, but the 4th does not. I will guess that this dot may be a decade mark, but I wouldn't know for which decade, as the time sequence for the first four pictures is as yet unknown. I also don't know if the 4-section circle around the triple-x has any significance.

In the last picture you can see two dots over the "T" and one dot over the "X" in TRIPLEX. This is a date code used after January 1969.

The date of manufacture is then defined by month rather then by calendar quarter. It is indicated by the dots over the word TRIPLEX as shown at left. This is where two dots over "T" and one dot over "X" means August.