Serial Numbers On Glass?

serial number glass

I worked on an absolutely beautiful 1984 Chevy Caprice recently, and noticed that it had engraved serial numbers on all the glass.  I understand why they do it, but is this common?  I have worked on about 11 trillion cars, and this is the first that I have seen like this.

Oh great 1AAuto Blog Readers, please school me on this. Common? Not Common? Does it actually thwart thievery? Is it just another way for dealers to grab money?  Who has this on their cars?

Bonus Note: That is me in the reflection, with the camera phone. Hi.