This constellation watch is up for auction in Japan and the back of the case has some sort of corrosion and discoloration. Does anyone know what could have caused this? And also, is it easily rectified? The rest of the watch looks fine. (The green circle is the seller pointing out damage to the strap). Thanks for your help

 

The purple stuff on the back is like a soft varnish that's used to stop handling marks before sale. It's possible that the other marks are just dirt/crud picked up or stuck to the purple stuff.

The seller could use a cotton bud and a drop of acetone to clean away a small spot to show it's not corrosion.

 

Looks like dirt to me. Let's see the front!

 

Yes - collectors affectionately call that stuff "purple snot". Ironically, what it means is not corrosion - but rather a perfect state of NOS-ness. It's factory applied, as stated above, to prevent scratches when a customer tries on the watch.

What this means is that the watch has never been worn. A fantastic sign.

 

Yes... I guess technically it could have been worn. But I was talking in the spirit of it being worn so few times that it might as well be assumed to have never been worn. There is no technical difference.

 

Some folks feel they are allergic to metal on the skin. Could be wax applied to isolate the skin from the metal back.

 

Thanks for the replies. It's a great help.