Maybe other DVDs are like this, and I just never noticed it before, but where the lettering is, you can see through the disc.  This is true on both the Blu-ray and regular DVD.  All this time I thought there was some extremely thin, but opaque, metallic layer sandwiched in the plastic that the 'data' was burned in to.  Guess I'd better do some more reading in the technology sector.  :^)

Yep. All discs are transparent. Usually, the disc art keeps you from seeing it, but it's noticeable if there's a lot of blank space.