Light is very degrading to paper...especially on a scanner -always best to photograph in daylight (no flash) when/if possible.
Ron..I think it's great that you held on to the calendar. Probably, many people wrote on theirs then tossed them at the end of '78 (along with their disco records and elevator shoes
).
And depending on how many were published -I would still think that it's relatively rare.
Wishing you many warm memories
