its rather parasitic diodes of the process, not really protection diodes. Normally the chip is not distroyed if the polarity is not reversed, or if the power is current limited to less than 50..100mA even if reversed.

If you place an Ceramic Eprom the wrongside into a socket, one or two bond wires will glow through the window like a small light bulb, this is may be a christmas application :)

the last application is: use the chip as a photocell. It will supply a couple of uAmps if held to a light. Maybe enough for the current of an RTC :) :)

I forgot the normal use of eproms, since flash has conquered the embedded world

Werner