Hi Erik
Girder forks is a term to describe the general type of fork of which the fork made by Percival Brothers and Webb was an example.
So it is a generic term
There were many different companies who made “Girder” forks
PB&Webb were perhaps the biggest company and made other items including brakes whick Scott fitted.
I use Webb Girder forks on my racer and like them.
Kind Regards
Roger
