Anyway, we appear to have identified the adapter part necessary to connect a POL (large bottle) female outlet to a POL (RV/small bottle) male connector. This is good because we'd be out a couple hundred dollars otherwise and be stuck with a bottle of propane we couldn't use.
I was amused to discover that one of the two standards for connecting propane bottles is called ACME. Surprisingly, it's the newer of the two, not one that was deprecated due to unfortunate incidents with a coyote.