Update:

This isn’t new.  Barry Schwartz from SearchEngineLand first noticed this in August:

http://searchengineland.com/google-checkout-steps-up-promotion-through-adwords-14635.php

We did suddenly see a rash of these on Monday, so perhaps the program was expanded.

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Google has consistently been increasing the visual differentiation of the badges in AdWords and are testing new badges with coupons prominently displayed.

Here is a screenshot:

This is apparently a limited test. This thread shows that not all merchants are permitted to use the badge.