Perhaps it is something screwed onto the left end of the hub .. Arai drum brakes for 3rd drag brakes , went on the same RH thread, as freewheels,

but being on the left , the Braking force tightened them on. so maybe it is a Widget screwed on to fill the space

and make people in the future wonder what it is ..



Those 4 holes in the face of it may be there to Unscrew It from the hub.. with a Pin spanner ..

Phil wood had a disc brake, the disc was made of the friction Material, the pads were steel ,
perhaps thats the core the disc spline fitted onto ,

wheels go on frames unrelated to the original choice..


I built a 48 hole Touring wheel around what likely in retrospect may have been the shell for a Phil Disc Font wheel

as It was single threaded .. PW Co pressed a rear axle assembly in it and it worked Fine ..