The Granite State Clean Cars Program (http://des.nh.gov/organization/divisions/air/tsb/tps/gsccp/) lets participating dealers put a special label in the window of new vehicles that meet environmentally superior performance ratings.
Links:
[1] http://des.nh.gov/organization/divisions/air/tsb/tps/gsccp/
[2] http://www.greenguidenh.com/content/374/car