Well, I had never heard of KKG before, but it is a possibility (for those who don't know, KKG (for Knallkörpergerät) was a device that allowed to clear acoiustic mines from the air, the same way that ring allowed to blow magnetic mines. See
http://forum.12oclockhigh.net/showthread.php?t=32522).
As the naval chronicle says Soviet airmen downed 3 Ju 52 equiped for clearing mines, they were probably equiped with rings rather than KKG.
And I always thought that Ju 52 MS in loss lists were the ones equipped with the big ring.