Read the Date Stamped on the Glass

A used car will tell you almost nothing about itself voluntarily. The odometer can be wound. Paint can be matched. A service book can be filled in on the morning of the sale. But the glass is different, because nobody makes glass to order for a resale. Every pane fitted to a car left a factory on a particular day, and it carries that day etched into one of its corners, along with the name of the company that made it. Six or seven small, independent, factory-applied dates, sitting on the same vehicle, put there by a supplier who had no interest in the price you are about to pay. That is an unusual thing to find in a used-car deal, and almost nobody looks at it.

What the Little Block in the Corner Actually Is

Look at the bottom corner of a windscreen, usually on the passenger side, and you will find a small etched or printed block of text and symbols. The trade calls it the bug, or sometimes the monogram. It is on the side windows too, and on the quarter glass, and on the rear screen, generally in a lower corner of each pane.

That block is a specification sheet in miniature. It typically carries the glass maker's trademark, the type of glazing, laminated or toughened, a part number, the country of manufacture, the certification marks the pane was approved under, and a date code that says when the pane left the plant. It is etched into the glass rather than stuck on as a label, which matters: a seller can remove a sticker, but not this.

The certification marks you will see on Indian glass

Safety glass for road transport in India is covered by IS 2553 (Part 2): 2019, which replaced the 1992 version of the standard and was notified in the Gazette of India in February 2020. Glass certified under it carries the BIS Standard Mark, the familiar ISI mark. Many panes additionally carry an international approval under ECE Regulation 43, which appears as a circled E with a country number alongside a 43R approval number, the maker's own mark, a symbol indicating laminated glass and a class for visible light transmittance. Glass made for other markets carries other schemes entirely; the AS1, AS2 and AS3 ratings you may have read about belong to the American system, where AS1 is the only rating permitted anywhere on a windscreen.

The practical point is not that a buyer should audit compliance. It is that a pane with no recognisable certification marking at all, on a car whose other panes carry one, is an anomaly worth a question. And it is worth knowing that CMVR Rule 100 requires the windscreen and rear window to maintain visual light transmission of not less than 70 percent, and side windows not less than 50 percent, so a pane or film that visibly fails that is a separate problem you would be inheriting.

How the Date Code Works, and Why You Should Not Trust One Scheme

The most widely used convention pairs a single digit for the year with a group of dots for the month. Dots printed before the digit mean the first half of the year; dots printed after the digit mean the second half. The dots then count downwards rather than upwards, so six dots is the first month of that half and one dot is the last. Six dots before the digit is January and one dot before it is June; six dots after the digit is July and one dot after it is December.

Which is exactly why the method that works for a used-car buyer is not decoding. It is comparing. You do not need to know that a particular pane says March 2019 in one maker's private scheme. You need to know whether all six or seven panes on the car carry codes that look like they belong to the same short window, and whether one of them clearly does not. A mismatch is visible even when the absolute date is not, because the panes are being read against each other rather than against a lookup table.

One Newer Pane Means Very Little. The Pattern Means a Lot

Here is where most write-ups on this subject overreach, and where a buyer should be sceptical of anyone who tells you a replaced windscreen is damning. It usually is not. A stone thrown up by a truck on the Mumbai–Pune expressway is the most ordinary damage in Indian motoring, and a windscreen that has been changed once in six years is a story about a highway, not about a crash. If you reject every car with a newer windscreen you will reject a great many honest cars and learn nothing.

The signal is in the pattern: which panes, and on which side.

• Windscreen alone, newer than the rest. Usually a stone chip. A weak signal on its own, and not a reason to walk away. Note it and move on.
• A side window and a quarter glass on the same side. Much more interesting. Two panes on one flank rarely fail independently. This is either a break-in or an impact, and both are worth asking about.
• Windscreen plus a front door glass plus a headlamp that looks newer than its twin. That describes a front-corner event with a location on the car. Now you are looking at panel gaps and paint on that corner as well.
• Every pane replaced, all clustered around one later date. Consider flood or a rebuild. Stop reading glass at this point and go and read the record instead.
• Panes newer than the rest but older than the car. Second-hand or salvaged glass has been fitted. That tells you something about how the repair was done, and therefore about the rest of the repair.

A break-in is the honest alternative explanation for a replaced side window, and it deserves to be stated plainly rather than buried: a car parked overnight in a Bengaluru apartment basement can lose a quarter glass to a thief with a spark plug and no accident of any kind. The pattern does not prove a crash. It tells you where on the car to concentrate everything else you look at, which is a genuinely useful thing for a buyer who has twenty minutes and a torch.

What sits around the glass, not just in its corner

The date code is one input. The installation is another, and it is often easier to see in a photograph. Glass fitted outside the factory is bonded by a person working against the clock, and the work leaves traces.

• Old adhesive or urethane residue at the edges, where the previous bead was not fully cleaned off before the new one went down.
• A urethane bead that is visibly wider on one edge than another, or that wanders where the factory line would be even.
• Visible gaps between the pane and the body, or a moulding that is not properly seated along one run.
• Trim clips that do not sit flush, or a beading strip that stands slightly proud of its channel.
• An aerial, rain sensor or camera bracket that has been disturbed and re-stuck a few millimetres off its original position.
• Reported symptoms that follow bad fitment: water seeping in during rain or after a wash, and a whistle or whoosh at speed where air is passing through a gap in the seal.

None of these is exotic. All of them are ordinary consequences of a pane being replaced by hand, and a buyer who has been told the car is untouched has a straightforward inconsistency to raise. We went through the same logic for bodywork in spotting a hidden crash from panel gaps and respray, and glass belongs in that family of evidence: small, physical, and hard to dress up.

Why This Is a Photograph Job Rather Than a Driveway Job

Reading glass codes is not difficult work. It is tedious work, and tedium is where human inspection fails. You are crouching at six different corners of a car, in whatever light the seller's parking spot offers, holding a phone torch at an angle, trying to hold in your head what the third pane said while you squint at the fifth. A buyer in Coimbatore who has driven forty kilometres to see a car, with the seller standing beside him and a second buyer supposedly arriving at seven, is not going to do that carefully. He is going to glance at the windscreen and form an impression.

Photographs change the problem. The corner markings and the trim around each pane are visible in ordinary listing images when the shots are close enough and clear enough, and a set of photographs can be examined in the same order, to the same standard, without a seller watching. Comparing six small etchings across a photo set for internal consistency is precisely the sort of patient, repetitive comparison an engine does more reliably than a person in a hurry. That is what our AI Vahan Inspection at Rs. 249 is for: it reads the seller's photographs alongside the VAHAN record and flags condition, mismatch and red-flag risks before you commit a deposit. Our note on what the Rs. 249 report actually covers sets out the scope in detail.

A photo-based check is also not the same thing as putting the car on a lift. It is earlier and cheaper, and it is meant to decide which cars deserve a workshop visit rather than to replace one. We compared the two directly in AI photo inspection against a workshop pre-delivery inspection, and the honest summary is that they sit at different points in the buying sequence.

The Glass Is Evidence of an Impact. The Record Is Evidence of a Claim

This is the limit of the whole technique, and it should be said plainly rather than glossed over. Glass date codes tell you that a pane was replaced. With the surrounding evidence, they suggest that something happened to that part of the car. They tell you nothing at all about what was claimed, what was assessed, whether the vehicle was written off, or what its registration status is today.

Those are record questions, and they have a different answer. A Vahan Verify RC Check costs Rs. 99 and establishes the registration date, RC status, fitness and insurance validity, owner serial and hypothecation against the registration number. The Challan Check also costs Rs. 99 and returns the pending challan list. The Full Report costs Rs. 149 and covers both; buying the two separately costs Rs. 198, so the Full Report saves Rs. 49. The registration date is the single most useful line for this purpose, because it is the reference point every glass date code has to be compared against.

Neither of these is a substitute for the other, and a buyer who does only one of them is answering half a question. A car can carry a spotless record and a badly repaired front corner; it can also have a replaced windscreen, a perfectly honest stone-chip explanation and an entirely clean file. We made that argument at length in why a clean RC is not enough on its own, and the glass case is one of the cleanest illustrations of it. For the records half of the accident question specifically, hidden accident claim history covers what the paperwork side can and cannot reveal.

How to Use This on the Next Car You Look At

1. Get the registration number and establish the record first. An RC Check at Rs. 99 gives you the registration date, RC status, fitness and insurance validity, owner serial and hypothecation. Without the registration date you have nothing to compare the glass codes against, so this genuinely comes first.
2. Ask the seller for a close photograph of every pane's lower corner. Windscreen, both front doors, both rear doors, both quarter glasses, rear screen. Frame it as routine, because it is. The speed and completeness of the response is part of the answer.
3. Compare the panes against each other, not against a decoding chart. You are looking for one code that clearly does not belong to the same window as the others. Do not attempt to pin an exact month from a scheme you cannot confirm the maker uses.
4. Map the odd panes onto the car. Write down which positions are newer. One pane in isolation is weak. Two on the same side, or a cluster around one corner, tells you where to look at panel gaps, paint texture, lamp clarity and shut lines.
5. Read the trim, sealant and brackets in the same photographs. Urethane residue, an uneven bead, a moulding standing proud, clips that do not sit flush, a rain sensor or aerial bracket that has been disturbed. Fitment evidence corroborates a date code far better than a second opinion does.
6. Run the photo set through an AI Vahan Inspection at Rs. 249 before you pay a deposit. It reads the seller's images alongside the VAHAN record and flags condition, mismatch and red-flag risks, which is the point at which a pattern across six panes stops depending on how patient you were feeling in the driveway.
7. Ask the seller directly, and listen to the shape of the answer. "Was any glass changed, and why" is a fair question. A stone chip on the expressway with a bill from a glass shop is a good answer. A blank denial on a car with one obviously newer quarter glass is a different kind of answer.

A Short Note for Sellers

If your car has had a windscreen replaced, say so in the listing, and say why. This is a pricing argument rather than an ethical one. Glass markings are permanent and factory-applied, and checks that read them are now cheap enough that a serious buyer may well have run one before they call you. A replaced windscreen that you disclosed is a stone chip. The identical windscreen, discovered by a buyer who was told the car was untouched, becomes evidence of an accident you concealed, and it gets priced as one, along with a discount for everything else the buyer now suspects. Disclosure costs you one line of text and removes an entire category of late renegotiation. When you are ready, you can list a verified car on VahanBazaar for Rs. 99.

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