Thanks for the suggestions. From the times you posted, I inferred "not wildly different from Efke 100", so gave it 7 minutes in HC-110 dilution B.
The results...well, the development looks reasonable, but the film is, as you might expect, a bit messed up. There's a bit of a light leak at one end (I assume from the box, which seemed seriously inadequate for light protection), some very large light streaks across the image, and a bit of random mottling all over the negative, including in the unexposed borders.
The result may actually look kind of interesting, but I wouldn't count on this film to produce a reasonable image of the object being photographed. However, this *was* the top sheet of a stack that didn't seem to be very well protected, and further down things may not be as bad. Research continues.
-NT