Do you want it for a shooter or collector? For a collection, you want the best condition (depending on other factors, like matching parts or mfg. date) possible. However, the M59/66's that are in best condition have been rebuilt, so that actually may hurt collector value-it just "depends."
For a shooter, personally, I woundn't pay an extra $40.
Also, take a look at Southern Ohio Gun. My current catalog has them at $149/good $159/excellent.