Mystery coating

I picked up a used, but almost NIB set of Williams passenger cars.  The wheel sets and pickup rollers show no marks.  Two of the cars have issues with the paint.  There is a coating that can be scraped off with a finger nail, but some looks like it reacted with the paint, much like using brake fluid to remove it.  What scrapes off looks alot like that very fine waxed rice paper you get from some Asian imports, especially tools.  It could also be the clear coat coming off if it that was applied.  Thankfully the cars are silver and the bad stuff did not cover up any writing, so light sanding and a re-coat should eliminate the issue.  Anybody run across a similar situation?