THANKS TO EVERYONE for such prompt polite answers. Yes, they must be
quince --- how I bought the tree as "persimmon" I'll never know.
The flowers' fragrance is not my favourite, and likewise, the only
time I tried to eat one of the fruit I didn't suit my taste buds
either.

I checked the leaves and flowers as well, on Google, as suggested, and
they match exactly.

Yesterday I had to bring down and throw away the remaining fruit, as
my annual visitor, a very fat black bear, had spent the night in my
garden creating havoc and pooping prolifically --- and householders
here can get a fine for leaving out bear attractants. Last year he
wrenched off a major branch, something the "darling little deer" did
to my apple tree too. The quince tree is not very big, perhaps
fifteen feet high, but produces about 130 fruit, which seems very
prolific.

Again, thanks for your help and pointers; now I shall ask some local
experts about quince --- perhaps it HAS been ripe and I didn't
recognize the fact ---.