A German stamp on cover with an o/p stating 30 June 1930.But the postmark on the cover reads as 31/10/29.Since the o/p on the stamp is 30 June 1930, isn't the stamp supposed to be used after that date for postage.With the thought that the cancel could be the other way around (yy/mm/dd),I checked and double checked my other covers and noticed that German postmarks or cancels reads as dd/mm/yy.Your opinions and assistance would be most appreciated. Thanks.

Closer view of the stamp and postmark.
