George, they are PROMs, they're really EPROMS without a window, and you could also get them with the window to make them rewritable. I'd have to find my UV chip eraser if I started tinkering with those old chips, I used to use tons of EPROMs, they were the Cat's Meow back in the 70's and 80's. When FLASH came along and the higher capacity chips that could be programmed in the device were available, EPROMs died out pretty quickly. A little known fact with those PROMS, you could actually erase them with heat, but it was a bit hit or miss. However, PROMs were cheaper than EPROMs as the ceramic package was the most expensive piece of an EPROM, the plastic package OTOH, was dirt cheap.
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