Like a lot of folks here, I'm the type of guy to keep all the wiring on a parts pin (or component), just to have stuff around if needed. Up until now, I have not bothered reusing coils since most of the ones I have from a parts pin have burn marks, but more & more I'm buying stuff that has coils attached, and they don't look all that bad, so they might be worth re-using.

I figure that just about the only thing that can be done is to check the resistance & inductance, and the diodes as well. I figure that so long as the coil looks good from the outside and passes these electrical performance tests, they are good to go.