Bernd brought up a good point that the gray surround on the cowl ring is certainly unconventional, and rare. I've never seen it as well. So I went looking for an answer.
There were 12 F4F-3 from VMG 211 assigned to Wake Island prior to the start of the war. On Nov 28,1941 11 of the 12 aircraft flew out to the USS Enterprise for the trip to Wake. The 12th aircraft had starter problems and didn't make the trip. All USN aircraft were still painted in the single mid tone Gray scheme.
While onboard the repaint orders were received to apply the new two tone standard colors. Since the single tone Gray was so close to the two tone Gray, and that the trip only would take 6 days, it was decided to only apply the Non-Specular Blue-Gray M-585/FS36118. Since the props were all on, and the time needed to remove them and reinstall them, they were left them on. Tarps were used to cover the props that were tied to the cowl. Hence, the cowl rings were also left in the Med Gray, and no two aircraft were exactly alike.
This also meant that the 2nd half of VMF-211 stationed at Hawaii had the regular two tone paint scheme applied, so that the squadron aircraft didn't match. That became a mood point after all 11 aircraft were lost or captured on Wake Island.