Manufacturer
The codes used to denote manufacturers were not unique to a single company as they were re-assigned, usually when the company had either ceased operations or had not produced an aircraft for the Navy for a considerable period of time. Additionally, aircraft built under license received a separate design number than the aircraft produced by the designing company. For example Goodyear produced Vought's F4U as the FG and Grumman's TBF torpedo bomber was produced by General Motors as the TBM. Foreign aircraft generally did not receive a designation under this system unless they were to be built under license in the United States, or were built in Canada for use in the U.S.
Read more about this topic: 1922 United States Navy Aircraft Designation System