MG FF
MG FF is an Oerlikon FF or autocannon.
Also recorded as Ikaria MG FF.
Overview
20 mm autocannon aircraft armament.
In detail
It is associated with Nazi Germany.
Sources
Each source is named with the standing the house places on it, so the evidence can be weighed rather than taken on trust.
reference work · Reputable secondary · Wikipedia
“MG FF cannon”, English Wikipedia, consulted as further reading
Consult the sourcereference work · Reputable secondary · Wikidata
Wikidata, structured authority record Q680704: MG FF
Consult the source