Hello Old Friend

[everettr]

Here is a minimally intrusive technique that you may want to try: leave the calculator out in the light. Recently, I received a rather nice HP 21s with some black blotches seemingly embedded in the LCD. The display was still usable, but unsightly. I took it to work and left it out on my desk for convenient use. After a week, I noticed the blotches were disappearing. After a month, the blotches were gone.
I remember that people recommended extended sun exposure for photographic lenses that had suffered fungal growths. Perhaps some blemished LCD displays will respond to similar treatment?