You made a good purchase with the AHS postmark. These sonderstempel were prolific during the Third Reich era. Today many are very scarce and some even quite rare while others are relatively common. Overall the Third Reich sonderstempel, postage stamps, and most covers (envelopes with sonderstempel and stamp intact) remain very affordable and have not inflated in price as has most everything else. In short they are an excellent value for the cost in my opinion.
One of the more interesting and less common AH special cancels or sonderstempel is one for Adolf Hitler Koog. Basically a koog is a landfill whereby an area covered by sea water is reclaimed by filling in with soil from elsewhere. The landfill and new area for this particular one was named for AH. It is there today but has a different name now.