<caveat first>I know that fig naming is inherently error prone and full of silliness</caveat first>
So, keep in mind that Nero just means Black. This name of Nero 600M seems to have stuck across a pretty wide swath of people, and the story about the 600m elevation is catchy, so that makes the name seem a little more exotic. Not sure how long that name has been around. It's a black fig that was found at an elevation of 600m above sea level. (But also, 600M is not really all that high up... in feet it's about 2000 ft... and given the latitude of that village, 2000 feet above sea level is not all that cold a place compared with where some folks grow figs). Anyway, my preference is for Valle Calde or ValleCalde (the Calde Valley) as a name I'd prefer, if it's the same fig cultivar. You mention that paully... do you know it to be an alternative name for the same cultivar?
And Mike in Hanover, do you have a reference for it being the same cultivar as Valle Negra? I have Valle Negra (the fig variety I mean... I don't own any land in the Black Valley in Lombardy), but I hadn't heard that it's the same as this cultivar that people call Nero 600m... do you know if it is, or have you seen a reference discussion on that? The leaves I've seen for Valle Negra don't look much like the leaves that paully shows, but I guess we all know just how misleadingly unreliable leaf morphology can be. But the fruits I've seen of Valle Negra (at least so far) don't look too much like paully's fruit either. Incidentally, in the name Valle Negra, I think the "negra" part of that didn't come about because it's a black fig (though it is). I think it came about because Black Valley (Valle Negra) is a local dialect usage for the name of the valley where it was found... Valle Camonica in Lombardia (Lombardy), Italy. See http://www.italia.it/en/travel-ideas/unesco-world-heritage-sites/valcamonica-the-rock-art.html or you can look on Maggie's fig site at https://sites.google.com/site/mediterraneanfloragarden/my-fig-tree-varieties (scroll down).
I'd be interested to learn if the Valle Calde variety and Valle Negra are really the same variety... I hadn't heard that. (Any reference appreciated).
Mike central NY state, zone 5a