I thought I would offer some observations regarding my III, even though it's earlier than the cameras in question at the top of the thread.
I have one chrome III, s/n: 1366XX, which puts it around 1934, acc'd to the tables at Cameraquest.
There's no brassing to the top or bottom plates from wear, although the base plate has plenty of light scratching, and there's enough wear to the upper sides on the holes in the body lugs to suggest that this Barnack didn't hide in an eveready case.
The RF / shutter speed "dome" does exhibit some pitting and peeling, here and there.
The worst pitting/ peeling is right around the serial # ( no signs of mischief), then around the bottom edges of the RF "dome".
There's some slight pitting of the top plate, around the three screws that secure the rewind knob bearing to the top plate.
The plating on all the knobs looks pretty sound.
This camera came from an E-bayer in Florida, and given the rusting I've found around steel screws in the body, I think the "rash" may be due to salt-air ?
Oddly enough, though this is the ugliest of my five Barnacks, it is in the best working-order: curtains are sound, and the shutter seems to be spot-on at all speeds, even the slows...
To sum-up, the "bad chrome" on this particular camera is mostly confined to the RF cover/ "dome"...
Luddite Frank
( mfr's info:
Ernst Leitz
Wetzlar
D.R.P. - stamped in RF dome; 3/8 "European" tripod-socket )