Catalogued as early as 1939, the OMIFO close-up accessory permitted fixed 1:4 ratio ( 1/4th life size) photos with the rangefinder coupled 9cm Elmar. The OMIFO was listed along with the OMAPO for the 5cm lenses. As far as I can determine, the OMAPO never reached series production.
Post World War II the OMIFO appeared in E. Leitz, Inc. New York price lists in June 1951. In May 1952 the OMIFO is listed as discontinued.
Leica IIIc with 9cm Elmar and OMIFO OMIFO on Leica IIIc 501476 (1950). Note sharkskin covering
Leica II with OMIFO and 9cm Elmar OMIFO engraving detail