California Black Plates -   The DMV here will take away ANY black plates you walk into their office with. Guaranteed!. However if you tell them your bike has no plates and give them a bill of sale they will gladly register it. Then you fill out a form for "year of manufacture plates" , give them the black plate you "found" , a check for $35 dollars and they register the plate to your bike. And charge you $11 a year to keep the plate.

There is a thriving legal market for black plates at swap meets and the like, but it is important to check and see if someone has legal title to the plates you just bought.