I searched and can't seem to find detailed info or pics about this watch. this is the first pic of the mythical PAM 523
Looks like it's a white dial version of the 510. Not sure if a link to the site is allowed, but it's a blog by the Sydney Tarts.
"Remember how I mentioned that brands were holding things back at SIHH? So they could possibly release these during/before Baselworld for thunder-stealing? some eagle eyed peeps on the forums discovered this gem! This is what we all wanted/needed from Panerai! In-house, 8 days, manual wind in a 44mm Luminor case. Looks to me the perfect replacement for the current ETA-powered PAM 111"
"There is also PAM 511, gold version, and PAM 523 with a white dial. I'm sure this is just the beginning as Panerai possibly start to phase out all the ETA-based models."