At first glance it seems that, in the Intel 82xx series of that era, only the 8255 (Parallel I/O Interface) and 8237 (Direct Memory Access - DMA - Controller) had forty pins.
Another candidate from those days could be the National Semiconductor 8250 UART chip ("one of the most prolific and most cloned UART chips", apparently ... and now lots of stuff on line), which also came in a forty-pin DIL package. Pin 20 is Ground, Pin 40 is +5 VDC.
UART:- Universal Asynchronous Receiver/Transmitter. An integrated circuit for implementing the interface for serial communications (eg, RS-232).
