Triplex dating code
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.From the dot over the "T", we know the glass was manufactured in the first quarter of the year (Jan-Mar).From the dot below the "U", we know the glass was manufactured in 1963.
Triplex Safety Glass is now owned by Pilkington, which uses a similar method of dating using dots under letters, but is not described here.
I believe the tempered glass is a newer contrivance which can be stronger and may be manufactured in thinner plate to be less expensive. The last four pictures came from a 1969 Rolls Royce, and the word "SUNDYM" is apparently a trade name for tinted glass.
Post war items are easily recognisable as from 1945 onwards the BS logo (or kite mark) was added below the original TRIPLEX logo. Notice in the first picture above the word AGREE with dots over the 4th and 5th letters.
A side issue of potential interest: Dating your car by its windows - based on the original compiled by Neil Cairns.
------ "MG's made in the 1950's to the late 1970's can be dated by the 'TRIPLEX CODE' etched into the toughened glass.The other four were supplied by Kevin Mc Cabe 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.