“Here we have a 4K SRAM from Cypress. Looks like the original design is from 1985, however, the date of manufacture is unknown. This chip was in a skinny DIP package but it was ceramic instead of plastic. I carefully opened the package using a chisel and hammer and was surprised that the die had a bubble of soft, clear material over it. It might be due to different mechanical properties of the ceramic case and the silicon. Regardless of the reason, it made it much easier to recover the intact die.”

Source: http://microblog.routed.net/2007/03/23/ic-friday-cypress-semiconductor-cy7c172-35pc/

Package

Die