https://www.infineon.com/dgdl/Infineon-STK12C68_64_Kbit_(8_K_x_8)_AutoStore_nvSRAM_Datasheet-AdditionalTechnicalInformation-v09_00-EN.pdf?fileId=8ac78c8c7d0d8da4017d0ecc045f45bf&utm_source=cypress&utm_medium=referral&utm_campaign=202110_globe_en_all_integration-files

That is a 64Kbit memory. The power pins are at the opposite corners so when installed backwards it reverses the power pin polarity pretty much guaranteed to kill the chip.

6264 is the generic part number for that kind of SRAM. If you want

FM1608 will probably work as an NVRAM, but I can't say for sure.

Those quantum trap NVRAM are a bit finicky. I tried to use one in the GTB sys 3 MPU that is not directly compatible with FM1608 and was having corruption issues at power up or down even with an extra cap.

The used pull FM1608 usually work okay. There is read/write endurance limit on the chip you don't know how much has been used up, but I really have never heard of one going bad in service that seems like an endurance issue, or any issue really. I asked Cypress why the endurance increased from a datasheet from 2004 vs 2016 or whenever the cypress rebranding came. They said the endurance rating is extremely conservative for worst case scenarios and in 2004 they where not ready to guarantee the life that they can now and the old date codes before the datasheet changed have the same endurance as the newer dated ones.

Give any used chip a good visual inspection. Sometimes you find a whisker of solder shorting two legs together that is hard to see.