No, there are not any external pickup markings to know the winder.
In the recent newsletter received from BKP, there was a surprising number of well known guitarists added to the list of users, it's what caught my attention the most in the news update.
I've owned 8 BKP humbuckers and 6 single coils, I bought 70% of them direct from BKP and the other 30% from dealers in the States. They all have the trademark BKP sonic signature and craftsmanship, none of them measured differently in these aspects.
The most beautiful pickup I've ever heard and owned in the world is the Apache neck, at the time I ordered mine Tim was on Holiday. Sorted. :)
When one understands who Tim is as a man and a pickup creator, there is no need to worry who wound it...Tim selected and trained the winder. 8)
As a last note on this subject, quite often when I call or email BKP or Tim directly...he's busy winding pickups.