Photograph the small marking in the corner of every window and compare them with each other and with the build date on the door jamb label. Original glass usually dates from around the same time as the car, so one window that is clearly newer is a reason to ask why it was replaced.
For this November 5, 2026 note, I checked the QuickFix Windshields guide to corner markings (updated September 6, 2026), the Fesler guide to reading the bug and the federal glazing standard, FMVSS 205 at Cornell LII. So, the steps below explain what the marking shows and what it cannot prove.
What the corner marking is
QuickFix calls the corner block the bug and describes it as a federal certification marking fired into the glass. It says a mark that is a sticker or peels off is not a compliance mark. Fesler says the bug identifies the glass maker, the safety class, a part number, the country of manufacture and, through a digit and dots, roughly when it left the plant.
Read the DOT number and AS class
QuickFix says the DOT number identifies the glass manufacturer, never the automaker, and that a windshield must read AS1 and laminated. FMVSS 205 sets the federal glazing requirements and also applies to aftermarket replacement glazing. A windshield marked AS2, AS3 or tempered is the wrong glass for that opening.
Compare dates, do not over-decode
Fesler explains that the date is usually a single digit for the year plus dots for the month, but QuickFix stresses that the dot scheme is a manufacturer convention. Rather than decoding one window exactly, compare all of them. The odd one out is what matters.
Run the five-minute test
QuickFix suggests photographing the block on all five or six windows, adding the build date from the door jamb label and looking for the window that does not match. Note whether that window also carries a different glass brand or automaker logo from the rest.
What a replaced window can mean
A replaced windshield is common after a stone chip or crack and is not by itself a sign of a crash. A replaced side or rear window, or several replaced pieces on one side, can point to a break-in or collision. Look for matching clues nearby, such as paint differences or uneven panel gaps, before drawing conclusions.
Ask the seller and the records
Ask why any newer glass was fitted and whether an invoice or insurance claim exists. Check whether the windshield replacement shows in the report, and on cars with driver-assistance cameras ask whether the camera was recalibrated after the work.
We are a licensed CARFAX and AutoCheck reseller, not affiliated with CARFAX, AutoCheck or Experian. Recent advertised pricing has been about $5.50 guest, $4.50 member or $6.75 for a bundle; confirm the price and included reports at checkout. A history report and a hands-on test answer different questions, so plan to use both.
Keep the history report in view
Glass dates say nothing about title brands or mileage. Check title data through NMVTIS, read our windshield replacement explainer for how glass work may appear in a report, and our paint-work explainer for related body repairs. Our VIN check before a test drive guide covers what to run first.
Use the result in the offer
One newer windshield with a clean invoice is usually a non-issue. Several newer windows on one side, plus paint or gap clues, call for an inspection of that side before you agree a price.
Check the glass itself
While you are at each window, look for chips, cracks, scratches from wipers and any cloudy edges on the windshield. Damage in the driver line of sight may need fixing. Note any pieces with a different tint or shade from the rest.
Ask for photos before you travel
If the car is far away, ask the seller to send clear photos of the corner marking on every window plus the door jamb label. It costs the seller a few minutes and can save you a trip. A seller who refuses gives you useful information too.
Record what you found
Keep the photos together with the inspection notes. If you later sell the car, the record shows which glass was original when you bought it, and it helps a shop order matching parts if a window breaks.
Remember what glass cannot show
Glass dates cannot tell you about the structure, the airbags or the engine. Use them as one clue alongside the history report, a panel check and the inspection.
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