Well done!!! I found what I need to have, indeed!
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Regards, Maurizio
Great Manual. It was exactly what I was looking for
Text excerpt from page 53 (click to view)
12 June 1987
2. Sixth Mirror Replacement
Remove the exposure glass. (Refer to �Exposure Glass Removal.�) Remove the lens housing cover [A] (4 screws). Then, shift the lens housing [B] fully to the left and the 4th/5th mirror assembly [C] to the right. Remove the sliding plate [D] (4 screws), and remove the plate springs [E] from the both ends of the sixth mirror (1 screw each). Remove the sixth mirror as follows: (1) (2) (3) (4) (5) (6) (7) 5. Slide the sixth mirror [F] to the right. Push it into the groove [G] at the rear. Swing the front end to the right. Pull it towards the front. Swing the rear end to the left. Push it towards the rear. Remove it from the front.
Replace the sixth mirror. (Do not touch the mirror surface with bare hands while installing a new mirror.)