[Hallicrafters] S-120 Front Panel Corrosion?

[Wj5mh at aol.com]

I just bought an S-120 from a garage sale for a weekend project (ya know, the 
kind of project that lasts a couple months), and I noticed some fine lines on 
the panel.  At first, I thought it was paint...like someone squeezed a tube 
of white paint over parts of the panel, but in very fine, random lines.

Looking closer, the lines looked more like very fine scratches made by a 
power etching tool.

I disassembled the panel, and found some of this on the backside, too.  I 
used some very fine sandpaper, but that didn't remove all of it, so whatever it 
is, is in the aluminum.

I looked at it under a magnifying glass, and these lines actually run under 
the labeling and light gray lines of the S-120 panel, so it's got to be 
corrosion.  The rest of the chassis is fine.  No sign or rust or corrosion.

Just curious if anyone else has seen this.  It's just something new to me.

Joe