I haven't lost my memory (but it keeps getting erased)

I have had this sitting in my "fun to look at" drawer for years (obviously).  It is a EPROM (erasable programmable read only memory) from the 1970's.  The chip had a quartz window (removed from this one) that allowed an intense ultrviolet light to be used to erase the memory on the chip.
 

For those who can't uncross their eyes, here is the red/green version:

You can go to Fickr for a closeup of the actual chip (it looks a bit like a football field).