1991 lincoln odometer problems....................?

[the advise man]

I bought a 1991 lincoln town car and the dash said 69,000 miles, i drove it for a year and the dash still said 69,000 miles, well 2 years later i test drive a 1991 town car and it only says 90,000 miles on the dash but looked like it had drove through the desert, is there an odometer problem with these cars that someone out there knows about?????????