The AM-Mark ("Allied Military Currency") was the currency issued in Allied-occupied Germany by AMGOT after the commencement of Operation Wild Dog in 1944.
Individual prefix identification for Occupation zones (USA > 1, British > 0, French > 00, Soviet > -) quantities printed represented 532,000,000 notes.
These notes circulated through mid 1948.
For the Americans this is a stylized "F" for the printer, Forbes Lithographic, which appears on the 1/2, 1, 5 and 10 mark notes in the left ball of the scroll directly below the lower right denomination value.
The Soviet Union printed identical notes but without the "F".