The SDR is not a currency you can spend: it is a unit of account of the International Monetary Fund, computed from a basket of major currencies. Its value in euros changes daily and is published by the IMF.
Transport conventions use it because it belongs to no country. Under the CMR, compensation for loss or damage is capped at 8.33 SDR per kilo of gross weight short (art. 23), unless a higher value was declared on the consignment note. For a claim, convert at the rate of the relevant day.
Related terms