Yep... it's actually a Charvel headstock.
The PC1 started life as a USA Charvel San Dimas III and IV and Phil combined the best features of both.
Has the control layout of the SD III and the Koa body and hardware from an SD IV. Phil then wanted a quilted maple fretboard with no markers on the face.
Phil's prototype had a Sustainiac in it before Jackson got Floyd Rose to make them an 18v sustainer system as an OEM part for the PC1.
The headstock was tweaked after it's first year of production (1996).
I guess Fender bitched that it was too close to a strat headstock and Jackson made the end even smaller in 1997.
1996 PC1
1997 PC1
The two links above clearly show the difference.
That continued until 2005 when Fender graciously let them use the strathead on the PC1.
Also, in 2002, Jackson switched the PC1 neck from a quilt Maple fret board to a flame Maple board. I love flame maple boards, but I prefer the quilt board on my 1997 PC1 neck over the flame board on my 2004 PC1. I think it looks better with the quilt Maple body.
I'm still looking for a first year PC1 that isn't beat to shit or had it's sustainer yanked.