One of the games that many consumer networking product manufacturers play is changing the hardware design of products while keeping the model number the same. And we're not talking about minor component changes, either. More and more frequently, manufacturers are changing entire chipsets with no change to the model number.
Having spent 20+ years designing electronic gear, I can personally attest to the need to make component substitutions. Sometimes it's because a product keeps selling long beyond its intended product life—and the life of some of its components.
Other times, large production runs reveal designs that didn't include enough margin to handle normal component variation. And sometimes the cost savings afforded by the switch to a lower-cost alternative are just too good to resist.
It's one thing to tweak a product based on a well-worn standard like Ethernet. But it's quite another to change entire chipsets in still-not-fully-baked products like draft 802.11n wireless routers and cards. But that's what vendors are doing. Let's look at some examples.