Old letters that are tattered and yellowing can be microfilmed. Negatives can be made from fading photos, and an interesting image can be rescued and computer enhanced to its original clarity. A provincial archives can direct you to local suppliers of acid-free materials, microfilming, and photographic reproduction. If one of the main purposes of your archive is to support marketing and outreach to your membership, then your archivist should consider mounting an historical exhibit. Since exhibits are exposed to risks such as theft and adverse environmental conditions, it is unwise to display the original document.
Copies are inexpensive to make and easier than originals to handle.
It is sometimes impossible to replace an original, but in most cases a copy can be quickly duplicated. An early history exhibit might include photos of the original office and staff, samples of old forms and letterhead, examples of old logos, and maybe newspaper clippings about the credit union's role in the community. Sports exhibits are always popular, especially when the members see themselves in team shots. Depending on the surface, panel or display module you use you can set it up in different locations. An early history exhibit can stand in any office or branch.