I've heard of that too, in fact someone tried to do it with my car when they found out it had two numbers. The "dealer" I bouhgt the car from schemed with a friend to try to title and register COX6002 in Tennessee based on some junk body parts they had, none of which contained a serial number. Tennessee was very liberal with titles in those days--you simply provided an affadavit that you had the car and they issued you a title. These two worthies then secured a bank loan with the "car" as collateral. When they defaulted on the loan and the bank tried to get their collateral, things hit the fan, so to speak, and the FBI was called in; bank fraud is a federal offense. I had already contacted Tennessee DMV and notified them of the fraud, so they rescinded the title.
None of this fraud pertains to the originality of my car. I have the total title/registration history of CSX2186 from MSO to current title, as well as the obvious overstamp of the serial numbers. I agree with Trevor, it was probably expediency in Thames Ditton. Either the car didn't sell at the Paris Show because a customer wanted a red interior, or Chardonnet preferred a red interior for the show. AC records show the two cars were produced at almost identical times. And SAI records state that CSX2186 was delayed due to the Paris Show.