This is Leland Palmer's car. It's a dark blue 1975 Chevrolet Caprice Convertible with a tan interior. I know for sure the year and model because 1975 was the year when Chevy did a facelift on the full size Bel Air, Impala and Caprice (NOTE: All the same car, just different trim designations) and the 1974's look totally different with a much boxier front end. It also can't be a 1976 because they never made a convertible that year and I'm sure it's a Caprice because they never made an Impala Convertible in 1975.

It appeared in the 8th episode of the second season on the show Twin Peaks. If y'all would like I could scan more cars from the shows.

Thanks.
http://www.imcdb.org/vehicle.php?id=160574
For sure it would be nice if you can provide more cars images