I think we should hold off on making the judgement that the pickup is aftermarket. The best way to determine this is simple (if the shop will allow it) and is to look beneath the scratchplate. Also look at the photo I've attached to this post - it was taken in 1977 when I was in junior high school and I'm playing my school's early 1970s Fender Musicmaster Bass which may have the exact same pickup. While the trombone slide hides most of the pickup, you can see what looks like the exact same black skirt and the large screw in the lower corner of the skirt, and the position with the thumb rest looks the same.
Here is what I know about the bass in the 1977 photo:
> My first year at the school was 1975 (I was a 7th grader) and I know of two other bassists who previously used the same instrument, dating it to at least 1970 or 1971.
> I began using the bass in 1975 because the bassist who was in 9th grade had just got a Gibson Grabber bass and he was using it rather than the school's Fender.
> I've seen one other photo of the same bass from prior to 1974 (on a Facebook page .. I'll look for it) and it still had the same pickup.
> At some point in time (most likely early 1978) I was being a typical kid and messed with the pickup height adjustment screws and the pickup dropped into the body. I took it to a music store in downtown Parkersburg, West Virginia called Powell & Clark Music, where they fixed while I watched. I remember the man who fixed it telling me that the pickup was made by Ovation, but don't recall if he said it was a factory upgrade or an aftermarket. I can't see a junior high school band program having that type of an upgrade made to a new instrument, so I'm assuming it was a factory upgrade. I do recall music stores bring instruments in for the band directors and students to try out; a fellow bassist purchased a Fender Telecaster Bass that way in 1979 or 1980.
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