This card appears to have been sent by a German PoW in Russia to a bank in Sweden about a money transfer between a German bank and a Russian bank.
Google has translated the German message to something like this: I confirm that I have received this from Deutsche Bank by letter of credit from the Russian Bank for Foreign Trade.
I've heard of British officers cashing cheques in Germany drawn on Cox & Co but this card suggests a more commercial transaction.
Any suggestions?
Relatives of POWs in Russia could send them money using a Swedish intermediary bank. This POW acknowledges receipt of the money.
He is in Serpukhov, near Moscow. I don't think there was a camp there, so he may have been a civil internee. The card was censored in Petrograd.
Mystery solved!
Many thanks for this.
Jim