For your consideration, here is an Apollo 13 Re-Entry Cover Envelope with Apollo 8 Stamp, postmarked April, 17th, 1970, Cape Canaveral, Fl.  It is in nice shape.  There is a little tanning on the envelope from age.  It will be mailed in a bubble mailer with foam core stiffeners.  Item pictured is the actual item up for sale and comes from a non-smoking household.  (366.56u-.32od) 
 

[Thanks for looking!]