@Rusty Traque posted:NP's FT's, F7's, FP7's and F9's all had D/B's. I see no reason why the F3's wouldn't. Overhead views are hard to come by, but in this shot of the 1947 NCL the D/B vents are (barely) visible.
Rusty
It took some docu-diving to find info that Actually! showed what you were talking about - where !!! barely!!! Visible !!!! The db vents are!!! Barely visible - just behind the cab / left from the horns.