Hermann Wachtendonk was definitely a Gausieger in that trade group in 1937 so that's a good start but the left half of the certificate (a large picture of AH) is missing:
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Sometimes that half was removed post-war (for obvious reasons).
have never owned a 37 doc so could not comment on its authenticity but the ones i do have from 38,39 etc are the same as the one gary shows , but a lot have the left hand page missing due to the pic