"its not a "washer", as such, it's the steel insert in the speedo gear housing.
It's there to stop the axle crushing the alloy.
See, also, 'Aligning The Forks, After Wheel Removal'
said the man who just over one year ago stated that his owned from new 45 year old 3C did not have one
FEB 28 2021..........."I have no washer between the fork leg and the speedometer gearbox housing, never had one since new"
said I the day after.....I beg to differ McStrap, the washer is sunk into the alloy speedo housing and takes the end load of the shouldered spindle, spreading the clamping effect, without it the speedo gearbox would become damaged rapidly, there should be a gap of about 2 or 3 mm between the fork leg and the speedo gearbox if your legs are parallel and straight, the last thing to tighten when assembling this area is the two pinch clamps on the right hand leg (stock caliper set up) and only once the legs have been settled, the disc caliper can often influence this especially if callipper adapters are used, so best done with the right calliper off its mount and clear of the disc.
I am not being nice to him am I ? no change there eh hamish?
CLEM