I obtained it from a local glass company, who probably cut it from a larger sheet that is about 1/4
of an inch thick. It may have been $50 for two sheets that cover both sides of an observation hive
that holds a single brood frame.  I use it a dozen or so times a year for presentations, and it
requires cleaning perhaps once or twice a year.  I assumed that I would only want to build one, and
have it last a lifetime, also I do get asked often enough if the bees can escape, and the laminated
safety glass makes a good talking point.

I made my box using red oak and ash. The window panels are held in a rail and stile type frame with
the frame portions unglued, so that when I remove the glass I can also remove all of the wood trim
that holds the glass in place.  The top of the box is held in place with two long square drive wood
screws.

If you like I could work up a few jpeg images to send.
/Curtis