speedometers ??

Tested a Nissan Patrol today and permanently fixed in front of the speedo was a Sat Nav, I could read the odometer and see it illuminated but could not see all the glass or needle,, presenter was not present and could not be contacted. Brake test by rollers, park brake decelerometer in workshop so could not see if speedo operated.RFR is obviously not working !!
Did not want to pull it off in case something broke so passed and advised. on getting Certificate out of printer noticed that this year and last three years mileage has not changed so speedo obviously(or at least odometer) not working ??
Now we are not allowed to remove panelling Etc. to inspect IE; engine covers, sill covers Etc.
So how does this one stand against panelling, fixed items Etc ??
what would you have done.