Toshiba SP-S2 System ROM on a 1FZS MVS slot.
SP-S2 is the name of the 128KiB ROM containing the 68k code for the system ROM embedded in some MVS systems.
It's mapped in the 68k's address space from $C00000 to $C1FFFF, and mirrored over to $D00000.
The dump is named sp-s2.sp1 in system ROM sets.
See System ROM.