Not a YB, 2/3 of my normals have head stamps like that, and the belly isn't even close. Sorry, but it is a nice normal :)
Here's my female YB head stamp
http://i49.tinypic.com/164cq1.jpg
Here's my female normal head stamp (similar to yours)
http://i49.tinypic.com/2hwilna.jpg
Same female normal's belly
http://i49.tinypic.com/vxbsm1.jpg
Here's my male YB's belly
http://i47.tinypic.com/2cf2xz5.jpg