Here is my take:
1) This looks like real leather, feels like it , with all the natural inconsistencies of leather.
2) This is vinyl/composite. It's consistency and tensile properties help to keep the shape of the pad tightly around the plastic frame.
3) This is either leatherette or similar, but not the same material as (1). It is much softer to the touch, even fragile. I would guess that it was chosen to dampen the reflections within the inner cavity of the diaphragm chamber; but that's just a guess.
My serial number is 2 digits.
From my experience with ear pads this pad is not only OK but excellent design. The pads are leather, that's where most friction happens. The flap (2) is best a resilient and shape keeper material. The lower part (3) needs to be softer for better sealing, but not much friction happens there, unless you take it off too often.
So from all accounts, comfort, durability, sound, so far this looks good. The pads filling matters a lot, too, and will affect bass a lot, especially with what looks to be an Onken loading for the driver, in the best Fostex and Sony tradition.
If my learnings from modding the TH900 apply, I would try to affect sound primarily by cups filling and pads filling. If you prefer less boom with lighter sound, use memory foam. If you want less boom, deep extension and bigger sound stage, use a flatter and narrower carbon foam filling. The shape you find in the TH900 mods thread.
However, I would be reluctant to do changes to this phone, with spare parts so expensive, in the consistent Sony tradition .
I don’t see why this headphone should cost much more than the TH900, probably it will end up around that.