A like-new 1956 shop manual came with my 1956 coupe when I bought it in 1973, and a friend gave me a 356 Erzatzteil Katalog that he bought when he bought his car back in the 1950s. I also have a fairy ratty 1953 Porsche shop manual somewhere. I have no idea what they are worth, but I've been taking care of them. I have them in sealed bags and haven't needed to open them in years - although I should look for that extensive chapter on corner balancing that Afterburnerboy swears is in the shop manual

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Here are pictures. I'm not taking them out of the bags for pictures because it's a pain to re-seal them.