Thanks for the info. I guess time and wear play a big role as to why they can sound different even if they’re from the same revision.
Let’s assume I can get NOS ones, are there technical differences that makes one revision sound better or worse than the other?
As I have the choice I would like to get the best sounding one for my LA2A (at least for my taste). I already have the black HA-100X but it sounds too dark, bass heavy and saturated for me (too vintage)
Inductance seems to be highest in the middle area, may make the cleanest low bass, may not. Usually inductance is fine in any of them. Treble will differ across the eras, that's a matter of taste. Differences in 2 from the same batch and same living environment are down to QC tolerances. I don't like the old saying "U Take a Chance", but it's the kind of thing that pops up with market saturated product criticism. FWIW. "U T C" really applies to anything old.