I have been looking at the methods for doing the grid choke measurement. There are a few issues, and I figure I might get a more elegant sol'n to some of them.
One complication is from the change in L due to signal magnitude. All the gap-free, butt stacked inductors I've measured and played with have a fair change of L v. signal voltage across them. With a current sensing R in series, it is fairly easy to do a running tally of displayed impedance. Small change in voltage will make small differences, and I don't feel like a bunch of silly gymnastics if it can be avoided.
One would be to measure L at several voltages and see what the slope of the line is and make small corrections. Or just do several measurements at each frequency. The latter is a bit more thorough...:)
Or I could just say the change in signal voltage is small compared to applied voltage. The DCR is comparable to the planned sense R, and sometimes quite larger.
Or I could just ask the manufacturer...but most don't even post Cw numbers.