Thanks to your very astute observations, I can concur.Decoded the serials myself. One is Week 1 October 2020 and therefore should be the new one, as the repair program states: BEFORE October 2020.
The other one is Week 4 September 2020. So very close. Depending how accurate their October 2020 time stamp is, could go either way.
I took them out, paired them. Still hardware version 1.0.0, shipping firmware was 2D27, updated within minutes to the newest (the spatial audio one).
The swap before wasn’t even 3 weeks ago, developed the usual ANC issues. Those were August And July 2020. I compared both under a microscope.
The July and August APPs had a flush inner vent with the white plastic surface. The ones I received today both seem to be every so slightly but cosistently recessed into the APP housing. IF it means something, then it’s probably to avoid direct vent contact with the skin of the inner ear.
My serial numbers decoded to week 37 (D) and 40 (H) - BUT! - Apple actually printed the date on my replacement boxes.
Under Assembled in Vietnam on each box label are 2038 and 2041 - my decoded weeks were off by one.
So I also have one in September (R) and one in October (L).
I also notice the difference in the inner vent recess with the new ones. Very nice catch!