The term triple plated gets thrown around as if it somehow the best kind of chrome when it is actually the industry standard. It simply means that there are a combination of three layers usually consisting of two nickel and one very small layer of chrome.
Copied this from a chroming forum:
The most important issue for durable chrome plating for outdoor exposure such as on a vehicle is that it should have at least two layers of nickel plating before the chrome: namely semi-bright nickel followed by bright nickel. The reason for this involves galvanic corrosion issues. The bright nickel is anodic to the semi-bright nickel, and sacrificially protects it, spreading the corrosion forces laterally instead of allowing them to penetrate through to the steel. OEMs demand very close control of this factor, and there is a test (the Chrysler developed STEP test) which large shops run daily to insure the right potentials. Careful control of this issue is probably the principal reason that today's chrome plating greatly outlasts the chrome plating of earlier times. If a restoration shop offers only single layer nickel plating, they must apply it really really heavy if corrosion resistance is to be guaranteed.
Experts argue whether copper plating provides any additional corrosion resistance at all, but with or without copper plating, chrome on top of a single thin layer of nickel will not hold up to the severe exposure of a vehicle! Industry professionals call the two layers of nickel "duplex nickel plating", and that would be a much better term to use than "triple chrome" and such.