First off great cabinets.
I would stack one on top of the other basing the stack order on which one would be used more often.
Are you trying to create some counter space for underneath?
For a mouth guard?
I bought a small one off of Amazon for 20-25.00 to clean my wife's jewelry. It works great.
As I understand it, they work the same. You just need a size that accomplishes your task (size of object) at hand.
Hopefully some of you who are more familiar with MAC can help date this box. The one I have is older with the nickel-plated handles made in 1965. My guess on this box is sometime in the 80's.
Either way you have to admit a great resto.