This offer is not limited to those with Kindle with Special Offers, but is open to anyone with a Mastercard (but ends at midnight tonight, Pacific Time, US).
Save $10 when you spend $100 with your MasterCard® card at Amazon.com. Plus, get an additional $10 discount on a future purchase.
When you click thru the link above, you'll see a group discount code. Use this promo code during checkout, AFTER you set your payment method to any Mastercard; you must use the full checkout process in order to enter your promotional code (no one-clicking). Also, like all Amazon sales that use promotional codes, if you have a gift card balance, you must use it for the payment - if you have more than a $100 balance, you may need to call and have your gift balance frozen while you enter the order; if you have less, whatever is there is used up first (so, you could put, say $89 on your Visa and apply it to your account as a gift card, then pay the remainder using your Mastercard).
You can use this one on any physical products sold by Amazon.com. You can't use it to buy gift cards, on any type of digital download or use it with one-click purchases (you must go thru the checkout process in order to enter the code) or on third-party merchants. You do not have to restrict yourself to the toys or other items shown at the bottom of the page. So, if you have some Holiday shopping to do, you might want to gather up several items into one order (and get free shipping, too) and use the code to get $10 off now and $10 off another order, later on.
This is a repeat of the last Mastercard Day and looks to have the same rules, so you know how it works, by now.