the devalued mark was pegged to the rentenmark at a trillion to one. The hyperinflation was over, and Germany was back on a gold standard system.
The Rentenbank apparently held no gold bullion. Instead, the bank held mostly debt, in the form of mortgages on property and bonds on German industry. The rentenmark was not redeemable in gold.
The main thing, with the Rentenmark, was that its value remained equivalent to a "gold mark." This was accomplished by reducing its issuance if there was any threat of its market value falling below that parity. The mechanism was simple adjustment of supply.
Farmers accepted the rentenmark in trade for their crop, and the crisis was resolved.