Here are pics of the books.
As can be seen on the warranty card, 37597 was delivered to Annette Hoheiser in Dusseldorff on 9 July 1981.
The first service in South Africa was at Basil Green motors in October 1982 so the car was likely exported soon after it was purchased in Germany.
I only have one set of keys and only the number on the door key matches the number in the book.
In the book, whilst some of the stamps are missing, I found that I have stamps for all of the mileage except for from 85,000 to 105,000 kms. I am going to call the service places in the book to get copies of invoices if I can.