How can one identify pickups from stock fender strats?

[bluelime]

For eg mij mia mim strats.
Lets say u want to sell the pickups to someone how can u prove that the pups is from ur mij 90s?
Or if u want to buy a pups how do u ensure that the pups is from a mia strat or mij or mim.

 

[bluelime]

Does anyone knows? since nothing marked behind them if i'm not wrong.