Is this also the 2-6MB Memory Expansion Option (6450367)?
Memory Expansion Adapter FRU 90X9507
J1-3 Burndy VH3X32S-2Z16
Memory Daughter Card FRU 90X9009
"IBM Personal System/2 A Business Perspective" 1st Ed., pg. 49, Fig 37, "Any Model 80 can accept up to three 80386 Memory Expansion Options." Memory speed is 80 ns.