Thought that others might find this information interesting and/or helpful. Window type eproms usually have a sticker covering the silicon chip to prevent erasure. Additionally, looking at the end of the eprom an extra layer can be seen in the cross section. I believe it's generally accepted that this layer is the window covering material. Most of us are aware of these facts. However, recently while looking over a board I saw an eprom that had this extra layer but no window. So I decided it was time to find out what was going on here. I pulled the eprom placed it on a stable metal surface and tapped it with a hammer. The top layer of ceramic fell away and there was a beautiful gold "window"! I then went to my bucket of IC's/eproms and began searching. At the very bottom I found another eprom with no window but the same cross section. Tapped it a couple of times and there was a silver "window". Maybe all eproms are made with the gold or silver in the middle. I don't know and don't care. I do know that the extra opaque layer allows the eproms I was working with to split open nicely. I see no reason why these can not be included in a batch of window type for sell on eBay or to whom ever. Photo quality is a bit poor but it will suffice.
Two ceramic eproms with and w/o window.
Cross section - gold window
Cross section - windowless. Had to reassemble for photo after splitting.
Windowless eprom after splitting.
Silver windowless eprom
Bookmarks