Each state has their own plate (with their own colors). Our plate numbers usually change every year unless the owner chooses to renew the old number. Our plates are only good for one year and are NOT transferable between owners. In other words, the plate belongs to the owner, showing he registered his car.
In the 50's and 60's, folks used to remove their old plate and nail it to their garage wall (or throw it in the trash).
When a car is sold, the plate is always removed but the plate's owner may apply it to another car he owns (like if he trades his old for a new car). If he doesn't transfer, the plate simply expires on his next birthday.
Every car swap meet I have ever attended always had someone there selling old license plates (spanning many years) for a few dollars each. If you ask 100 people here, what number was on the first plate of their ten year old car, none of them would know because it simply doesn't matter.
In Michigan, we can use any plate from the year our classic car was made. We call that a 'period plate'. Again, all those original records were destroyed long ago, so nobody knows (or cares) what car the old plate came off of. It simply needs to be in good shape. If not, some restorers repaint them to the original colors. Obviously, approval will not be granted for a number that is currently registered.
I don't personally don't know anyone who had a plate custom made to look like a period plate because there are so many out there and they are inexpensive.
Our state offers 'personalized' annual plates for a fee. We submit a suggested (tastefully done) number with remittance and they either process it or reject the submission. - Dave