Measuring inductance of powdered iron toroid

[Circlotron]

I have several powdered iron toroids that I need to identify. One I think is 220uH according to the manufacturer. I don't have an LCR meter so I thought I might just put a cap in parallel and apply an oscillator and see what frequency it resonates at. Is this really suitable or would the inductance be specified with a certain amount of DC current bias? If so, what would the error be? Just a bit off or totally way out?