Fred, Brandon, Spiro, Thanks for all your answers.
operating system called NextStep. It sounds like they came up with a variety of site-local address pre-RFC1918 and pre-RFC3927 that did something similar to RFC 3927 addresses.
That's it. 192.42.172.0/24 is often used in examples, but I also found in the "Automatic Host Addition" chapter of http://www.levenez.com/NeXTSTEP/netinfo_user_guide.pdf the following: "The second property, configuration_ipaddr, is required and specifies the address that must not be allocated by nibootpd. This address is in fact the address that NeXT uses to identify a new workstation temporarily during the boot process. It should always be set to 192.42.172.253 explicitly." It looks like this /24 is (was) a must for their "Automatic Host Addition" process. So now I see how this prefix got into Barry's list. Andras