RHD cars had a letter R before the engine serial number. The car number, if you can find it, is different from US production. I was told a car number tag should be on or near the front seat frame of my '31 phaeton assembled in Argentina. I have examined it carefully and cannot see any evidence that there ever was a car number tag. Some other differences I have found; the water pump is a completely enclosed casting, the bottom piston ring is located under the wrist pin, the speedometer reads in kilometers, a small hole for vacuum wiper is on the right side. The windshield frame can be reversed to relocate the wiper to the left side. Also see if the instrument panel appears to be modified where it's bolted to the steering column.