Speedometer conversion?

[the_webbster]

Here's a good one:
I'm looking at a 1980 euro spec 930 which has 52K miles on the speedometer. the seller is advertising the car as 52K miles but does not have any service records for the car, only the handbook and manuals in the glovebox.

So my question is:
what about the mileage on the KM speedometer which was taken out?

Is there any way to research how far the car has gone? how about the import documents? seller has those.

help!