Pogo has re-released 50 previously-retired Mix-n-Match badges which are on sale for 12 gems each until June 7th.
To find these badges easier, sort by "Retires" and look for the badges marked "Re-released".
These badges were originally released in February 2007 and April 2018.
https://www.pogo.com/challenge/find-badge.do?searchtype=mnm&sortName=expires&sortDirection=true
(https://i.imgur.com/PtPs4Ko.gif)
You're welcome!
Tx