The really daft thing is to all the comments above about the car, the owner could go out and buy a damaged, stripped or rough 500, like the recent black one on ebay, stamp the blue shell with the 500s chassis number quite legally (its not ringing if a new shell is used), scrap the old shell and suddenly it is then a genuine RS500, even despite the fact the engine is not to 500 spec - he could join the RSOC with it and Paul the RSOC register would have no choice but to to say it is then in fact a genuine RS500.
All for the sake of 5 minutes with a set of stamps from Machine Mart this car would go from a really dissed home build to the real deal. As Andy said his was inspected by the DVLA but this rarely happens with other reshells, even dealers reshells dont get inspected and sometimes dont even get stamped.