Robb, they are possibly a pretty broad spec - this one is a hair thinner at 7/64". Mind you, while it is old and pitted and appears original I can't be 100% sure it is.
I assume the spacer is needed to provide clearance between the mudguard stay and this type of brake cable adjuster.
Never to old to learn, I didn't know about these. I did find a drawing of this distance piece. The drawing could give an idea about it's dimensions as it has a hole for a 1/4" bolt. I have the drawing from the 1940 parts list.
They might not have been fitted on bikes with a brake rod, there is only need for this distance piece is when the cable adjuster is located on the brake back plate.
I didn't know about that one either..I have fitted a spacer there to space the mudguard stay off the cable adjuster in the past..without realising there was supposed to be one!...Then I started to use a cable with a smaller hexagonal adjuster and locknut which solved the problem and I removed the spacer...Now I am missing the spacer AND probably have the wrong cable adjuster.. ..Ian
Between the toolbox and clamp or between the bolt and clamp? I can't really see why there should be a spacer there but I do want one if it should be there.
Many thanks! This is good info for me and getting my bike correct. Ian, I appreciate your comment on the front brake concerning this little piece of steel.
I also agree that "between the "P" clamp" would be
great as my clamp from Russells (1978)is a bit cranked, and it looks like you need the spacer to give room for the tool box to sit squarely.