Standard Modular System (SMS) card of unknown function. There are discrete transistors and other components covering the board. There are two of these modules. Each has an opaque cover over the components. The model number 5300011 is printed in solder on each of these modules.
International Business Machines (IBM)
Stamped on the component side at the insertion end
Printed on the solder side and stamped on the component side at the insertion end