I Necro-ing this topic, because after researching mine, I found this thread most enlightening.
Here's my story:
I bought a Zoo Keeper conversion (previously in an Alpine Ski cabinet which is vertical). And someone prior to the previous owner cut a hole and added a bubble. My guess is that the original vertically mounted monitor fit, but when it crapped out and it was swapped with another, the frame prevented the door from closing. So they used a hole saw bit and drilled 3 holes and cut the rest out around that. Looks AWFUL. Turns out it was too close to the lock, so they had to cut a piece off of the bubble itself to make it not cover the lock when installed. Again, I hate how it look both on the outside and inside.
Luckily, it closes just fine without the bubble. So I'm going to replace the back door with something made from scratch sans the bubble. I will use the old door as a template, minus the hole of course.
I guess my mystery is solved then. I was wondering if the bubble was stock or added afterwards.
Pics below for reference on mine.
Del