Say WHAT!!!

[GG]

Question is, is that stuff removable? 

You have a great opportunity to find out, because it's gotten onto two of the ribs inside the phone, on either side of the main area of the spot.

What I'd suggest is to try the peroxide goop on the innermost edge of *one* of the ribs only, and then compare the outcome to what it "should" look like.  Then do the other rib and compare further.   Then do the inside of the stain and see how that comes out, starting with a weak concentration of the goop and brief periods of application, so you can go at it by slow degrees and get it just right. 

If all of it comes out OK with no damage or white blotches, then it might be worth attempting on the exterior of the phone. 

[Jester]

GG,
I'm right with you on that!  Since I got this one, I've been wondering if the peroxide treatment would improve it or restore it.  I have some other projects I've been meaning to treat, so I might throw this cover in, too.  Stay tuned!

[Greg G.]

I'll take this slightly used one that I lost out on for over $900 less!

http://tinyurl.com/5ropq9x

What does the "62" below the manufacture date signify?

[Jester]

This is one of those rare instances where the color code was stamped on the base.  This one is the only one I've seen this done to that was not made in 1956 or earlier.  Most of the time, you will only find the color code stamped on the dial.

[jsowers]

the "62" below the manufacture date signify?

The -62 is the WE color code for aqua blue. That's not often seen on the bottom of 500s and very seldom on a phone made this late. I have a red one with a 53 on it. I'm not sure why only some have that because usually it's on the back of the dial mechanism

Sorry, Stephen, we both posted the same thing at the same time and it didn't show me your post. My red one is a 554 from 1-56 and the only 554 I've seen with a color number stamped on the back. I found a picture of it, posted below. Note that even the "-" is there.

[JorgeAmely]

I'll take this slightly used one that I lost out on for over $900 less!

http://tinyurl.com/5ropq9x

What does the "62" below the manufacture date signify?

That is the color code for Aqua Blue. I have a Mahogany Brown phone with the color code stamped on the base as well. Kind of rare to see bases with color codes stamped on them.