This set is often referred to as the "MAME 2000" set because it reflects the state of MAME at the turn of the millennium. The reference set ensures that every ROM matches the exact checksums (CRC/SHA1) expected by the 0.37b5 driver, eliminating the common "missing files" errors seen with mismatched versions.
: Each version of MAME requires ROMs from a matching "romset." The MAME 2000 emulator core strictly requires the 0.37b5 set and will generally not work with newer versions like MAME 0.139. MAME 2000 Reference Set - MAME 0.37b5 ROMs and ...