OK, I just tried some Kieffer pears from a farmer’s market recently - and I think that’s what my mystery pear was! The general shape, skin texture, and (crispy, gritty, watery) taste all seemed to match! Which would all basically attest to its suspected Eurasian (European Pyrus communis + Asian Pyrus pyrifolia or ussuriensis) heritage:
Thus this new hybrid, thought to be a chance cross between a [Chinese] sand pear and a Barlett, became known as the Kieffer Pear.
So, mystery finally solved now (I think)!!! 