60s P90 pickups: black bobbin vs clear bobbin - any difference?

[Guitar Magic]

Does anyone know whether the black bobbin and clear bobbin P90 versions in '67-'68 have any difference besides the cosmetics? I owned a '68 Goldtop which had a factory black and a factory clear bobbin P90. Recently, I've just acquired a '68 SG Special with untouched electronics and both of the P90s are the earlier black bobbin ones. Any constructional difference between the two that we know about (wire, magnet, anything)?

If they are the same, do you have any info when the constructional changes took place in the manufacturing of P90 pickups? Will the P90s in a 63-65 SG for instance will be different compared to the ones in a '67 SG besides the obvious lack of the wooden spacers? What are the main differences?

 

[Wilko]

I don't know of any difference. Clear are later though. Maybe started as early as '68.

Mike Campbell's '72 has clear bobbins. (it's often called a '68, but it has all '72 features. Confusingly named by Gibson "Les Paul Custom '58"