1946 Occupied Germany "condemned" marking

[dmui]

Here is an item that has eluded my efforts at explanation.

The commercial post card from Brussels to Germany datelined and postmarked September 16, 1948 shows an American Zone censor marking with #15674 , assigned I believe to Esslingen and a circular 508 handstamp which I think was a Belgian censor marking. Of note is a "Condemned" marking on the left side with a manuscript "PEX 1" and "Trade" and initials MM.

I have had no success in locating information about any "Condemned" marking in the post war era.

Can any of our members help with this puzzling card?

Thanks Dave