Its just an older blade and bolt set. They are basically the same as current sets.
Washer onto Bolt,then bolt through blade then insert into the base. Then felt over bolt on the other side,then dust cap over felt,then finish of with the nut. The felt was coated in oil and kept the bolt to blade surface dust free and lubricated. Thats it.
The dust cap and felt actually resemble the inner wheel dust caps which also used the same principle of lubrication and stopping dust from scoring the axle.
Anyways a cool find.
Im sure I still have at least one blade plate in my pile with these on them.
They did away with the dust caps early on, and were eventually replaced by std bolt sets you see today.
