I have packed up my mineral collection for storage. these old wall cases date to 1914 when the store opened. Back then they held china dinnerware, crystal, silverware , flatware , clocks & pocket watches. The glass fronts lift straight up.
The glass is as old as the cases! they came with ripples & bubbles!
Interestingly, when viewed at a 90 degree angle the distortion almost goes away. the photo to the left was taken at a 10 to 20 degree angle.