I don't think it's chrome. I think it's either heat treatment or cobalt plating, but chrome seems unlikely to me.
I'm sure what Fo's referring to is this sort of thing:
![[SOLD] Model M 1391401, $61 shipped (U.S.)](https://geekhack.org/index.php?action=dlattach;topic=87520.0;attach=159944;image)
...vs. this:
![](http://img.photobucket.com/albums/v331/laurie47/DSC00120-2.jpg)
Yeah, it's always fun to open a board and see that beautiful lustre.
BTW, I neglected to mention that this listing says:
Keyboards are fully tested and cleaned thoroughly before shipment.
There's no telling if "fully cleaned" means they took off the top and cleaned the barrel plate. (Either one has a 5.5mm thin-walled hex wrench, or one doesn't—it's not one of those iffy things.) But at least key-cleaning wouldn't be necessary.