I have a manual on fiche - March 1978 rev 1 06268-90001 (paper)? 5951-6173 (fiche)
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Have scanned (hopefully) relevant pages here - ?Files? -> A temporary directory for photographs and help relating to emails and posting? -> HP 6268A
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If no one on the group can find the whole thing scanned online then I can scan it properly and post
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Peter