I discovered there is a way to estimate the resonant frequency of a guitar pickup using an "oscilloscope octopus" and a signal generator. This is
handy for when you have pickups with unknown specs and want to get an idea of their characteristics. Contrary to popular belief, DC resistance DOES NOT
tell you everything there is to know about a guitar pickup.
This method also works on things like wah pedal
inductors and small audio transformers.