The 9557F-SE is a SCSI terminator for
terminating SCSI LVD & SE bus systems.
Every SCSI subsystem must have a terminator
(terminating resistors) at each end of its
internal and/or external bus.
This terminator is mounted on a DH68F connector,
so it can plug into an open (male) connector on a SCSI
68-pin ribbon cable.