This is xnu-6153.11.26. See this file in:
Directory listing for xnu-6153.11.26//bsd/conf
Makefile
Makefile.arm
Makefile.arm64
Makefile.template
Makefile.x86_64
compat_hdrs.awk
copyright
files
files.arm
files.arm64
files.x86_64
param.c