1965–1972
Protect-O-Plate
A small embossed metal or plastic plate, physically like a credit card, issued with every new GM car from 1965 through 1972. Dealers stamped its embossed data onto warranty paperwork with a mechanical imprinter, which let GM validate warranty claims without looking the car up separately.
What it records
- Vehicle serial number
- Engine build date, type and horsepower
- Transmission type and build date
- Rear axle ratio and build date
- Exterior colour and interior trim codes
- Build month
- Carburettor type
- Installed options
Where to find it
Issued with the owner's paperwork, not fixed to the car — which is why so few survive with the vehicle. When a car sold, the dealer added the buyer's name, address and sale date on a Dymo label.
A Protect-O-Plate is loose paperwork. It is straightforward to pair one with a car it never belonged to, so it corroborates other records rather than standing on its own. GM discontinued it after 1972.
All
Build and broadcast sheets
Paperwork that rode down the assembly line with the car, telling line workers what to install. It was never meant to stay with the finished vehicle — the intended practice was for a worker to discard it at the end of the line.
What it records
- The options and equipment scheduled for that specific body
- Sequence and scheduling information used on the line
Where to find it
In practice sheets were frequently stuffed somewhere in the car and never removed: behind a seat, in the seat springs, under the dash, inside a door panel, or lying on top of the fuel tank. Survival is strongly plant-dependent — Los Angeles (Van Nuys) cars more often have a sheet left on top of the gas tank, while Norwood cars very rarely have one at all.
"Build sheet" and "broadcast sheet" are related but distinct documents with overlapping, not identical, information. The Norwood-versus-Van-Nuys survival difference is informed enthusiast consensus rather than a counted statistic, so a missing sheet on a Norwood car tells you nothing.
1967–2016
Service Parts Identification label
A label listing most — not necessarily every — factory-installed option by RPO code, alongside the VIN and paint/trim codes. It existed so dealer service departments could order the right parts without disassembling the car to check.
What it records
- VIN
- Paint and trim codes
- Most factory-installed options as RPO codes
Where to find it
Location varies by generation. The back of the glovebox door is the most commonly cited spot on first- through fourth-generation cars, with door jamb and trunk-lid or spare-tyre-cover locations also used depending on year. In 2017 GM replaced the SPID label with a QR-code label on the driver's-side B-pillar.
The label lists most options, not all of them, so an option absent from a SPID label was not necessarily absent from the car. It is also a label — replaceable, and reproduced commercially.