DAV is very guarded with the covers returned with contributions: Perhaps extremely protective of its contributors, DAV does NOT make "used" covers available to collectors.

However, DAV covers showing postal usage are available to collectors albeit not with their intended usage. 

Recipients of DAV solicitations sometimes use these franked return covers to send other letters.  The DAV address is crossed out or written over and a new address is added.  Such covers are eventually delivered to the new addressee but they first take an unintended detour. 

Because the covers are preprinted with the bar code of the DAV, USPS automatic sorting equipment reads that the covers should go to the DAV and so they do.   Along with thousands of similar covers containing contributions, these non-DAV intended covers are opened "accidentally" before it is discovered that they are addressed to other recipients.  Notice the neither cover has the Facing Identification Marks (FIMs) now required by USPS to receive the highest discounts for presorting outgoing mail.

The opened envelopes are sealed at the bottom with transparent tape and the message "OPENED BY MISTAKE BY D. A. V."  is added before being reentered into the mail stream. 

Of special interest to collectors of USPS spray cancels is the unusual repeating "CINCINNATI" spray which also ties the 5¢ stamps to the cover.