Yup, peeled knuckles. And what's worse is, they look pretty darned tasty:
Evidently, they can be cut into strips and stir-fried to near perfection. But I've shopped for groceries extensively on the border, where these were found, and there is a dearth - indeed, a world-class drought - of fresh Asian vegetables suitable for stir-fry there.
They must star in a Mexican dish of some sort. I'll knuckle down and get us an answer.