I thought I remember seeing some that did not have a retaining clip. one side was 'spring loaded' to make the pins spread if the other side plate was not on and this spring tension held it in place. but it was a basic oval plate and not typical "8" shape of most side plates
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk