The CostCo card is a completely different product from the American Express Platinum charge card.

What I don't get is why AmEx insists on calling so many of their credit cards "platinum" (They also have an Optima Platinum, a Cash rebate platinum, a Delta Skymiles platinum, and a Hilton HHonors Platinum card). When none of these have any of the benefits of The Platinum Card (which is a charge card, not a credit card).

It would be interesting to see if you could sneak into a WC with one of the "plat" credit cards, though. I would think there must be some receptionists who wouldn't know the difference, no?