F4F-3 Late production

[RTY1941]

To find out a F4F-3 (Late) was easy (PS:By watch the Engine Cowling) But later I check the BuNo numbers , I find out F4F-3 (Late) are BuNos 3856 to 3874 and 3970 to 4057 , but there's a surviving example is "Bu.4039" but it was not using F4F-3 (Late) Engine Cowling , so I want to know is that "Bu.4039" is a F4F-3 (Late) , can somebody help me ?

[The Inspector]

Go to Joe Baughers site http://www.joebaugher.com and select NAVY AND MARINE s/n 1911 to present