Citrus ID (pomelo / mandarin hybrid with a bit of a neck)

[JSea]

Hmmm. Trying to identify this unknown Citrus.

It peels reasonably easy even though the fruit was unripe. The juice vesicles are firm, like a pomelo, and the membranes are very thick. The fruit was not fully ripe, but tasted sort of like weak grapefruit / mandarin flavour, slightly more sweet than sour.
Approximately 30x seeds in one fruit, and up to 12 segments.
Zest smells kind of 'spicy' and more like an orange/grapefruit (not lemon).

Thinking it might be either kinkoji, sanbokan or possibly ujukitsu. Possibly there's other options as well.

[Scipio]

From the shape and the taste with a little grapefruit bitterness I would say that is the Kinkoji/Bloomsweet. Cannot be Ujukistu, it would be more elongated egg-like and mostly sweet with just a little sour hint.

[70Malibu]

Kinkoji, Marumero
Citrus obovoidea hort. ex I. Takah. RUTACEAE
CRC 3465
PI 539458

https://citrusvariety.ucr.edu/crc3465

[70Malibu]

I have Sanbokan, the fruit does not look like that, it has a neck lick sumo.

https://tropicalfruitforum.com/index.php?topic=45969.msg456210#msg456210

[JSea]

Thanks for the extra opinions folks. It's also my current conclusion that it's most likely kinkoji.

One thing I can add is that it seemed to be relatively weak when grown as seedlings - all of them died!! I grafted one to trifoliata and it's still alive but pretty slow growing so far.
I note the UCR link says "an excellent quick decline indicator for seedling yellows". Relatively mild strains of CTV are present almost everywhere in New Zealand, so I wonder if it could've been that.