Old paper made from rags is much more stable than modern papers, specially those from second half of XIXth century, and war periods. Some acidic inks could give problems, but that would be visible by now. Enclosing in plastic could be problematic if you live in a humid area and mold developes. Probably the worse problem could be silverfish insects (lepisma), because they can ravage single leafs and it is better to avoid sunlight. Leather bindings are a different matter, but you do not have that.
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