Odometer Reads 9,000 miles on my 1981 280zx?

[Isaac_Tran]

So I just got my 1981 280zx its pretty rough but its 5 speed manual that runs and drives for $800. They guy said in the add that the car had 90,000 miles and I didn't notice the car read 9,000 miles. what does this mean could he have rolled it back or did he replace the dash. The title says nothing about the milage. Is there anything I can look at to gauge its milage. how can i check to see if the dash was replaced or tampered.

 

Also does any one know how the check button works on the dash? Evenm when the engin is running it doesn't do anything when I press it. Is it broken or is there somthing else I need to do