WM1 x 21" Front Rim - Full Width Hub

I am trying to obtain some definitive data on Norton 'Export' Rim Sizes, particularly the American Desert Sleds. To that end:

1. What Models of Norton had a WM1 x 21" Front Rim laced to a Full Width Hub?

2. What year/s did this occur?

3. What is the Norton Part Number for this rim?