The FK 7M85 was designed to a requirement issued in 1944 for a dual-purpose anti-tank and artillery gun that could be produced quickly. The gun, cradle and recoil system from the 7.5 cm PaK 40 anti-tank gun was adapted to the 10.5 cm leFH 18/40 carriage. Interestingly the leFH 18/40 carriage had been itself adapted from the PaK 40 so this design essentially returned the gun to its original carriage, albeit modified with an extra 20° of elevation.
In 1944–45 the Germans changed their system of artillery designations from the old "year" system. Each weapon was to have a number showing their caliber group, a letter denoting ammunition group, and the last two digits were from the weapon drawing number. In this case 7 denoted 75 mm caliber using the M group of ammunition. The shells were all to be designated as M with a 4-digit number, the first three were the drawing number and the last was the shell's category from the following list:
Engelmann, Joachim and Scheibert, Horst. Deutsche Artillerie 1934-1945: Eine Dokumentation in Text, Skizzen und Bildern: Ausrüstung, Gliederung, Ausbildung, Führung, Einsatz. Limburg/Lahn, Germany: C. A. Starke, 1974
Gander, Terry and Chamberlain, Peter. Weapons of the Third Reich: An Encyclopedic Survey of All Small Arms, Artillery and Special Weapons of the German Land Forces 1939-1945. New York: Doubleday, 1979 ISBN 0-385-15090-3
Hogg, Ian V. German Artillery of World War Two. 2nd corrected edition. Mechanicsville, PA: Stackpole Books, 1997 ISBN 1-85367-480-X