Recently took la Duchesa to Mark Gray for a check over.
Whilst checking he said he thought that the base unit was non U.K. spec . given that the bumper mountings were different. He checked the base unit number inside the boot and confirmed it looked like the base unit was for a non U.K. spec. car, but was it was an unusual beast as it was right hand drive. The base unit number may be 7 BA-026280. I have added a pic but the definition is not great. If there is no number 7 there, then it still has the bumper fixings which by rights should not be present.
As I understand it may decode as: area USA no aircon (7) Buick (B) Automatic (A) 26,280 (022280) from the start of production. Speculatively this may mean a base unit intended for an LHD export car, became a RHD home car with the VIN 42516969 meaning a UK Three Thousand Five 17th from the end of production - 42516986. To add further to the interest the engine is suffix C which is compression ratio 10.5:1 but intended for series 2 cars! The windows are coded 1970 but the rear quartelights are fixed!
This is all a bit academic since the car is great and it does not matter very much about the origin. It is just a bit of added interest.