I got hold, finally, of a Cayman GatorBox CS, with its manuals and software (in a rather fetching binder).
You will often find this listed in lists of "LocalTalk bridges", along with things like the little AsantéTalk bridges, but this is a much more powerful device than that. First, it's a full AppleTalk router with an ethernet port and a LocalTalk port. This means that unlike, say, the AsantéTalk, this will actually work on networks with other AppleTalk routers. It will also act as a MacIP gateway, and do the same job of de-encapsulation for IPX and DECnet.
So far, so router-y. But this also has a couple of applications (if you paid for them!) specifically to bridge Macs to UNIX networks. It will, for starters, proxy between UNIX lpr printing and AppleTalk printing, making lpr PostScript printers turn up as LaserWriters. It will also, more interestingly, proxy NFS servers to AppleShare!
The one I have has both printing and share bridging preinstalled, but even if you got one that hadn't, netopia made the software available for free a little while ago.
One further interesting thing is that the configuration is as Mac-like as they could make it. You do not use a command line tool to configure it: instead, there is a configuration tool that works via the network which provides a rather Finder-like view of the GatorBoxes available to be configured:
When you double-click on one, you get a hierarchical icon-based view of the configuration:
And individual leaves in the configuration are configured through suspiciously compact mac screen sized dialog boxes: