55SX - BIOS model 'F8', BIOS sub-model '0C': 

27C512 x 2: 33F8145/33F8146 - 11/02/1988, Revision 0
27C512 x 2: 92F0626/92F0627 - 11/02/1988, Revision 0
27C512 x 2: 33F8102/33F8103 - 01/07/1989, Revision 1


55LS - BIOS model 'F8', BIOS submodel '1E':

27C512 x 2: 84F6896/84F6897 - 02/08/1990, Revision 0


55LS 486 (same planar as Reply 55, different BIOS):

27C1024: 02M3251 - Unable to directly read