"shamu" for Nexus 6
7.0.0 (NBD92F, Apr 2017)
7.0.0 (NBD92G, Apr 2017)
7.1.1 (N6F26Y, Apr 2017)
https://developers.google.com/android/images#shamu
https://developers.google.com/android/ota#shamu

Android Security Bulletin?April 2017
http://source.android.com/security/bulletin/2017-04-01.html