The Naval aircraft Factory complained to the Bureau of Aeronautics that they didn't subscribe a contest when they gave Grumman a contract to develop the F2F. When the USN wanted a successor for the F2F, they asked Grumman to develop the F3F and gave NAF the opportunity to compete with it.
the NAF started to work on the XFN-1 but weren't able to match a sufficient engine to their full-metal design and asked for support with the Seversky company.
So together they delivered the XFN-1 to NAS Anacostia. The plane was able to compete with the F3F but what the Navy didn't like was the fixed landing-gear. So they asked NAF to change the model with a retractable gear.
And so it happened that both NAF and Grumman were contracted to deliver a fighter to the Navy. The NAF-Seversky FN-1 was delivered to the carriers as a fighter/bomber.
In this way a new line was developed which ended with the navy variant from the P-35 (the F2N). More to come...
friendly regards
Lauhof