Wasn't it Noah A who wrote:

>i was looking at one just the other day and noticed that the protective glass
>has a purple oil on it or something

That's not oil, it's the antireflective coating. It works by an
interference process, similar to iridescence. It causes the reflected
light to be dimmer and purpler than would be expected for that type of
glass. I suppose the refracted light thereby becomes very slightly
yellower.

-- 
Mike Williams * ##
Gentleman of Leisure

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