FWIW:
Chris, wassup? I thought you were the one that straigthened me out on these things. Here's a cut from my review on the Bart:
Interesting pup and not quite your typical MM Bart in tone or appearance. Smooth face with an apparent line (not textured) running the length between coils and no logo. The back is epoxied - no copper backing plate.
I got from someone the SD doesn't have the line (which is same color as the pup but readily apparent).
No doubt this could be different for different periods.
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Chris, by the way, landed a 4 lead LP MM - reasonable (for an LP) no less.