i *think* i remember a guitar and bass article about fender pickups from a few months back, and i *think* i remember reading that the backs of the pickups changed in the 70s- or the pickups got worse, certainly, at some point (and i imagine the backs changed as this made them easier to distinguish).
Found it! Guitar and Bass Magazine, Feb 2009 (vol 20 No 3): according to that Phil Harris guy (who's their vintage guy, I think) in 1964 the pickups had a greeny-grey base, which changed to grey in 1971. Apparently the quality of the pickups got worse in 1975-76, when they changed to flat polepieces. Unfortunately, it doesn't mention the colour of the base. And of course, you have to trust Phil Harris's words- but i'd trust him more than that guy who clearly wants to buy your guitar.
i agree with philly, in other words. Do you have that issue, philly? If so, maybe you could check it to make sure I haven't missed anything, I'm not exactly a vintage gearhead... :lol: