Taken from an OmniKey 102.

Bottom case markings:
GT6OMNIKEY02
Part no. 560,0005
Vendor code 777
Serial no. 05056x-0G
Rev no. 3.04

Green PCB markings:
891120 rev. 0.0 OmniKey EXP/Plus
Patents Pending 1989

Tan PCB markings (This 102 has two parts.  Top PCB is green.  Bottom PCB is tan and screwed into the bottom case.)
PN 890717-00 rev. 01
OmniKey Plus/102 Controller 9023
Northgate Computer Sys. Inc. Patents Pending 1989.

Top (plastic) case date "dials", L to R:
90
7
6
(I assume this is July 06, 1990)
