Chris,
I think the answer lies either in his service details. As you are aware in many cases the recipient received a riband immediately on the award , which he wore on his tunic, a long time before he received his medal. If he were to be missing, wounded, or P.O.W. it is possible he never received his gold medal due to this and was given the bravery medal at the end of the war when repatriated or recovered. Or the other possibility is that the during the severe hyperinflation of 1923-24 when by the end 5 billion (that is 5 million million) marks were worth 1 US dollar. He may have been forced to pawn/sell his gold medal in order not to starve.
That's my 2 pfennigs worth.
All the best,
Paul