The 1965 and 1966 LeSabre are similar but this one is a 1966. It's not a Sedan but a 4 door hardtop (model 45239 or 45439), the sedan has smoother angles at the rear door windows.
Here are pictures to compare the 1965 and 1966 models.
1965 Wildcat 4 door sedan model 45469 (same roofline as the 1865-66 LeSabre 45269 sedan)
Here's a picture of my 1965 Wildcat 4 door hardtop model 46639 (again, has the same roofline as the 1965-66 LeSabre 4 door hardtop)
Note the shape of the front bumpers on 1965 Buicks
Here's a picture of a 1965 LeSabre 400 convertible to show the emblems on the rear quarters of the 1965 LeSabre.
Now a picture of my great uncle's 1966 LeSabre Custom 4 dr. Hardtop model 45439 to compare the LeSabre badge
The 1966 LeSabre 4 dr. hardtop roofline again
Now a picture of a 1966 Wildcat to show the shape of the 1966 front bumper (again, the LeSabre has the same).