Models 56SX/57SX and 56SLC/57SLC (8556/8557) BIOS Versions:

855x-x4x = Intel 386SX-20 (typically "C-STEP")
855x-x5x = IBM 386SLC-20

'U55'

92F1600 - Unknown date and revision
10G5029 - 12-07-1991, revision '09'