Typically had a heavier copper/nickel undercoat beneath the chrome.

This produced a warmer, slightly “deeper” chrome tone and better resistance to pitting.

Suppliers were still using plating standards developed in the late 1960s, before cost-cutting pressures.

GM began shifting contracts to different suppliers, especially as production volumes increased.

Nickel undercoats were often reduced in thickness, with more reliance on chrome flash for shine.

Result: brighter appearance out of the box, but more prone to corrosion in harsh climates.

Some plants also experimented with different polishing processes, which altered reflectivity.

Regulatory backdrop

The early 1970s saw new federal crash and corrosion standards. GM was preparing for the 1973 “5‑mph bumper” rule, which drove changes in bumper design and plating.

Cost and environmental pressures (EPA plating bath regulations) also nudged GM toward thinner, faster plating cycles.