As @usbfl astutely points out, the design of the phone is certainly a bit of a cross between the Nexus 4 by LG and the iPhone. There is a glass back which is consistent with the earlier rumors and renderings, and from what we can tell from the image, there also appears to be a fingerprint sensor on the back.
Now there is a bit of inconsistency in some of the rumors. Earlier there were rumors that the Nexus Sailfish and Marlin would be made from different materials, but as per the latest rumors, it has suggested that both phones will be made from the same materials and will also sport the same design.
Ultimately we could be looking at an iPhone-like situation where HTC/Google will offer up more or less identical handsets in different sizes, appealing to users who might prefer a smaller (and possibly cheaper) phone, or someone who might prefer having a larger display and might be willing to pay for it.