another mystery chip manufacturer
@tubetime Signetics, I would assume. Although not the most frequent logo
https://en.m.wikipedia.org/wiki/Signetics
@tubetime seems to be from Solidev, it's a "Triple 3-input NAND gate":
https://www.bg-electronics.de/datenblaetter/Schaltkreise/CM4000serie.pdf
@tubetime Signetics, I would assume. Although not the most frequent logo
https://en.m.wikipedia.org/wiki/Signetics