Date: Elul 5571
From: Rabbi Moshe Sofer
To: Rabbi Yeshayah
The Chasam Sofer rules that demand-payable debts actually demanded before the Austrian Finanzpatent of 1811 are repayable in devalued old banknotes per decree number 17. In iska arrangements, the loan portion converts per the decree while the deposit portion is valued at its original gold-coin value, with any subsequent commodity loss falling on the investor; he recommends settling and restructuring a new iska. Old currency still in circulation is governed by dina d'malchusa dina.
Source: Shu"t Chasam Sofer CM §63