Macca's zero fret mod

[Maccaguy]

I noticed the deep slots, too. It definitely doesn't have the white nut before the Abbey Road sessions, and as long as the original black nut was there, I'd bet there was no zero fret.

Since Paul used the Hofners during Let It Be, I wonder if he had the Ric stripped during this time, which resulted in a broken nut? Whomever replaced the nut also installed the zero fret.