IBM 3 User Manual page 302

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4247 Model 003 User's Guide
replace the ribbon cartridge.
3. Align the pin on the left and right side of the ribbon cartridge with the slots
in the cartridge supports.
4. Insert the ribbon guide between the ribbon shield and the printhead. Position
the white snap arm with the small lever up onto the ribbon lift assembly.
Push the white plastic arm down onto the ribbon lift assembly until it snaps