Looks like it's been pretty much covered now.
I will add that the Signature also has the pearl "R" on the head stock and the neck volute under the nut area.
Although a one or two Signatures were made with a top wood laminate on the backside of the head stock (as well as the top side) when Keith ran out of pearl material for the "R".
My newest Signature, built 2014, has the laminate on the backside or the headstock and the recessed control knobs. I think the volute is standard on the custom now.
Mark
Now I want to install 3-way mini switches in my Spanish Cedar fretless!!! Somebody stop me!!!