Charles Wright is a reasonable modern font to use, although I consider it more a post-war style; pre-war the figures such as 2,3,6,8,9 & 0 tended to have a much rounder profile. Hand-painted lettering almost always adopted a very 'circular' profile, and cast-alloy plates and those with individual cast letters were usually similar; the squarer-style similar to Charles Wright seems to have developed in the late-1930s with the pressed-alloy plates.
A quick search through photos of my old cars produced the following:
Hand-painted:
1969 crop (2).jpg (Size: 20.84 KB / Downloads: 220)
Image3 (2).jpg (Size: 24.88 KB / Downloads: 220)
IMG_5247 (2).JPG (Size: 24.46 KB / Downloads: 220)
cast-alloy:
019 (2).jpg (Size: 26.2 KB / Downloads: 220)
2018-06-20-0003 (2).jpg (Size: 19.99 KB / Downloads: 220)
rear (2).JPG (Size: 27.56 KB / Downloads: 219)
individual cast-alloy letters:
006 (2).jpg (Size: 22.49 KB / Downloads: 220)
1986 Malvern (2).png (Size: 26.23 KB / Downloads: 220)