There are 4-1/4" and 4-3/4" wide variants'
The 4-1/4" have:
1. NARROW bridge & stays, in short and in longer versions.Short for the "S" bike and normal/long for other series 1 models.
2. WIDE bridge and stays for series 2- 71 drum brake models and skinny front tires.
I believe this is correct as follows:
4-3/4" fenders with wide bridge and stays are for the larger front tire disc brake front ends.