The ESX900 is a heavily modified TH900 that cost $500 extra when it was available. (You can do a search and find lots of info, but bear in mind that there are different versions of the mod with various sound signatures.)

This ESX900 uses an original TH900 as its base (so red cups and hardwired 1/4" stock cable) and is an early "bass edition" that reportedly has stronger bass than later ones.

It comes with a headband cover, the original packaging and Fostex ST300 headphone stand.

It is in good condition except for the ST300 stand. (I never used the stand, so this was someone else's doing.) What looks like a cup scratch in the first photo is just a reflection. And of course, camera flashes emphasize dust.

I believe you can still send in the headphones to the modder (etaheadphones.com) to be retuned to your preference. (Not sure how much it would cost.)

I may be willing to do a trade, especially for a Fostex TH900mk2. (The regular non-modified version with red cups and detachable 1/4" stock cable, ideally with the original packaging and stand.) But feel free to make any offer.