You guys were correct - there is a small NPT fitting on the side. The chuck is pre-tensioned with a pin wrench, and the tightening ring is free and moves. Here are some more pictures. I probably won't be able to take this over to an air source until after T-day, but I'll swing by when I can if folks would like to see a video of it working.
Also, it looks like there is a model stamped on the bottom - MEAD 152
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