I didn't know Google gave Map Makers special certificates.
A picture on Flickr by Artjom Troitski shows a a gift given to one Map Maker including T-Shirt, Two stickers and a certificate.
Adam Lasnik of Google signed the certificate. FYI, Adam worked under Google's Matt Cutts several years back until switching roles in the company a few years ago.
This is the first time I've seen a certificate for Map Making on Google.