Such bars would not be to the 99.9 percent gold standard set by the London Bullion Market Association. They would instead be at about 90% purity, since American gold coins had 10% copper added, which makes the gold harder and more wear-resistant.
See https://www.bundesbank.de/en/press/press-releases/bundesbank... however, no explanation is given, only that the bars were melted, purified and then recast.
https://www.bundesbank.de/resource/blob/743058/9869caef634ce... - Federal Reserve Bank of New York starts at page 2016 (PDF:2019)
I think this list is not only used for internal audits but also to assure the public and banks that Germany indeed knows in detail where its gold is stored.
¹) https://www.bundesbank.de/de/aufgaben/themen/bundesbank-schl... (in German)
... to put it mildly. Nobody has audited the gold in decades and even its owners (banks of foreign countries) are not allowed to inspect it.