Analog Devices Logo in Center Middle.
Label:
5 3 4 8 F
Newer map: https://siliconpr0n.org/map/ad/ad534/mcmaster_mz_mit20x/
Old map: http://siliconpr0n.org/map/ad/ad534/mcmaster_unitron/
Datasheet: http://www.analog.com/static/imported-files/data_sheets/AD534S_die.pdf