Quick question about the HD650's

Hi. I received my HD650's a couple of days ago, and I was tremendously happy. I haven't even gotten around to trying them yet, as I'm still waiting for my amp. (Decided to go for the Asgard.) Now, I'm fairly new to this, but I'm sure I've read something about some fixes/tweaks/improvements being made to the HD650 cans somewhere along the way. What were these about? And when did it happen? I'm curious because I want to know if I got the "old" or the "new" cans, and if this matters. Is there any surefire way of knowing mine isn't a pair that has been collecting dust in this shop since before the fixes? Fabric number, perhaps?

Thank you for any input you may have

PS: A slightly unrelated, and probably stupid question: What is the desirable ratio between windows volume and amp volume when it's all set up? I have a Xonar DX dedicated soundcard (I'll probably get a DAC further down the road), and with no amp (and my old headphones), 30-40% is usually pretty loud. Should I hover at a low or high windows volume when I get my amp? Is there a sweetspot, perhaps, where the volume tuner on the amp actually has a range that makes sense?

Alright! Thanks a bunch. I looked through the mesh, and the screen inside was metallic/silvery in color, so I guess that's a good thing, then. And as soon as I get my Asgard, I should turn my windows volume to max and adjust at the amp, got it.

Thanks again for a helpful response.