This is a photo of my plates with screws. My TR3A came like this in May 1958 when I bought it new. The upper number late was painted body colour by Mulliners who made the bodies, semi-assembled it all and sprayed the whole thing. The brass plate was screwed on during final assembly.
The lower brass plate is a substitute and I had a new brass one made by Frank Angelini in Downingtown, PA with the correct numbers. But I have always had (and used) the original screws. On my TR3A, the screws were different for the two plates.