I wouldn't bother with EXACT readings as there are too many variables to stipulate a precise figure.

What you are looking for is a SHORT circuit (0 (zero) ohms) between the collector and emitter of the transistor. The transistor acts as a switch and when ON it basically shorts C to E - when OFF C to E read open circuit.

With power removed - if a transistor reads zero ohms between C and E it is stuffed and the coil will lock on as if the transistor switched it on.

That's what you need to understand and go from there.